diff --git a/docshell/base/nsDocShell.cpp b/docshell/base/nsDocShell.cpp
index ff04e25362..a2e24483a1 100644
--- a/docshell/base/nsDocShell.cpp
+++ b/docshell/base/nsDocShell.cpp
@@ -16,6 +16,7 @@
 #include "mozilla/dom/Element.h"
 #include "mozilla/dom/TabChild.h"
 #include "mozilla/dom/ProfileTimelineMarkerBinding.h"
+#include "mozilla/dom/ScreenOrientation.h"
 #include "mozilla/dom/ToJSValue.h"
 #include "mozilla/dom/workers/ServiceWorkerManager.h"
 #include "mozilla/EventStateManager.h"
@@ -757,6 +758,7 @@ nsDocShell::nsDocShell()
   , mLoadedTransIndex(-1)
   , mSandboxFlags(0)
   , mFullscreenAllowed(CHECK_ATTRIBUTES)
+  , mOrientationLock(eScreenOrientation_None)
   , mCreated(false)
   , mAllowSubframes(true)
   , mAllowPlugins(true)
@@ -2560,6 +2562,18 @@ nsDocShell::SetFullscreenAllowed(bool aFullscreenAllowed)
   return NS_OK;
 }
 
+ScreenOrientationInternal
+nsDocShell::OrientationLock()
+{
+  return mOrientationLock;
+}
+
+void
+nsDocShell::SetOrientationLock(ScreenOrientationInternal aOrientationLock)
+{
+  mOrientationLock = aOrientationLock;
+}
+
 NS_IMETHODIMP
 nsDocShell::GetMayEnableCharacterEncodingMenu(
     bool* aMayEnableCharacterEncodingMenu)
@@ -6065,6 +6079,16 @@ nsDocShell::SetIsActive(bool aIsActive)
   if (mScriptGlobal) {
     mScriptGlobal->SetIsBackground(!aIsActive);
     if (nsCOMPtr<nsIDocument> doc = mScriptGlobal->GetExtantDoc()) {
+      if (aIsActive) {
+        nsCOMPtr<nsIDocShellTreeItem> parent;
+        GetSameTypeParent(getter_AddRefs(parent));
+        if (!parent) {
+          // We only care about the top-level browsing context.
+          uint16_t orientation = OrientationLock();
+          ScreenOrientation::UpdateActiveOrientationLock(orientation);
+        }
+      }
+
       doc->PostVisibilityUpdateEvent();
     }
   }
@@ -10270,6 +10294,22 @@ nsDocShell::InternalLoad2(nsIURI* aURI,
     mTiming->NotifyUnloadAccepted(mCurrentURI);
   }
 
+  // Whenever a top-level browsing context is navigated, the user agent MUST
+  // lock the orientation of the document to the document's default
+  // orientation. We don't explicitly check for a top-level browsing context
+  // here because orientation is only set on top-level browsing contexts.
+  if (OrientationLock() != eScreenOrientation_None) {
+#ifdef DEBUG
+    nsCOMPtr<nsIDocShellTreeItem> parent;
+    GetSameTypeParent(getter_AddRefs(parent));
+    MOZ_ASSERT(!parent);
+#endif
+    SetOrientationLock(eScreenOrientation_None);
+    if (mIsActive) {
+      ScreenOrientation::UpdateActiveOrientationLock(eScreenOrientation_None);
+    }
+  }
+
   // Check for saving the presentation here, before calling Stop().
   // This is necessary so that we can catch any pending requests.
   // Since the new request has not been created yet, we pass null for the
diff --git a/docshell/base/nsDocShell.h b/docshell/base/nsDocShell.h
index 0fc5be6ddf..3fbcd654d9 100644
--- a/docshell/base/nsDocShell.h
+++ b/docshell/base/nsDocShell.h
@@ -62,6 +62,7 @@
 namespace mozilla {
 namespace dom {
 class EventTarget;
+typedef uint32_t ScreenOrientationInternal;
 } // namespace dom
 } // namespace mozilla
 
@@ -879,6 +880,10 @@ protected:
   };
   FullscreenAllowedState mFullscreenAllowed;
 
+  // The orientation lock as described by
+  // https://w3c.github.io/screen-orientation/
+  mozilla::dom::ScreenOrientationInternal mOrientationLock;
+
   // Cached value of the "browser.xul.error_pages.enabled" preference.
   static bool sUseErrorPages;
 
diff --git a/docshell/base/nsIDocShell.idl b/docshell/base/nsIDocShell.idl
index 6513268031..2816a1878e 100644
--- a/docshell/base/nsIDocShell.idl
+++ b/docshell/base/nsIDocShell.idl
@@ -46,7 +46,7 @@ interface nsITabParent;
  
 typedef unsigned long nsLoadFlags;
 
-[scriptable, builtinclass, uuid(97471054-0BC8-4A57-BBFE-6C255BCBBB67)]
+[scriptable, builtinclass, uuid(35a26f70-dbb9-450d-b634-cd0bbb9b8e13)]
 interface nsIDocShell : nsIDocShellTreeItem
 {
   /**
@@ -920,6 +920,9 @@ interface nsIDocShell : nsIDocShellTreeItem
   
   void setFullscreenAllowed(in boolean allowed);
 
+  [notxpcom] uint32_t orientationLock();
+  [notxpcom] void setOrientationLock(in uint32_t orientationLock);
+
   [noscript, infallible] attribute boolean affectPrivateSessionLifetime;
 
   /**
diff --git a/dom/base/ScreenOrientation.cpp b/dom/base/ScreenOrientation.cpp
new file mode 100644
index 0000000000..ca24ca57fa
--- /dev/null
+++ b/dom/base/ScreenOrientation.cpp
@@ -0,0 +1,645 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "ScreenOrientation.h"
+#include "nsIDeviceSensors.h"
+#include "nsSandboxFlags.h"
+#include "nsScreen.h"
+
+using namespace mozilla::dom;
+
+NS_IMPL_CYCLE_COLLECTION_INHERITED(ScreenOrientation,
+                                   DOMEventTargetHelper,
+                                   mScreen);
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION_INHERITED(ScreenOrientation)
+NS_INTERFACE_MAP_END_INHERITING(DOMEventTargetHelper)
+
+NS_IMPL_ADDREF_INHERITED(ScreenOrientation, DOMEventTargetHelper)
+NS_IMPL_RELEASE_INHERITED(ScreenOrientation, DOMEventTargetHelper)
+
+static OrientationType
+InternalOrientationToType(ScreenOrientationInternal aOrientation)
+{
+  switch (aOrientation) {
+  case eScreenOrientation_PortraitPrimary:
+    return OrientationType::Portrait_primary;
+  case eScreenOrientation_PortraitSecondary:
+    return OrientationType::Portrait_secondary;
+  case eScreenOrientation_LandscapePrimary:
+    return OrientationType::Landscape_primary;
+  case eScreenOrientation_LandscapeSecondary:
+    return OrientationType::Landscape_secondary;
+  default:
+    MOZ_CRASH("Bad aOrientation value");
+  }
+}
+
+static ScreenOrientationInternal
+OrientationTypeToInternal(OrientationType aOrientation)
+{
+  switch (aOrientation) {
+  case OrientationType::Portrait_primary:
+    return eScreenOrientation_PortraitPrimary;
+  case OrientationType::Portrait_secondary:
+    return eScreenOrientation_PortraitSecondary;
+  case OrientationType::Landscape_primary:
+    return eScreenOrientation_LandscapePrimary;
+  case OrientationType::Landscape_secondary:
+    return eScreenOrientation_LandscapeSecondary;
+  default:
+    MOZ_CRASH("Bad aOrientation value");
+  }
+}
+
+ScreenOrientation::ScreenOrientation(nsPIDOMWindow* aWindow, nsScreen* aScreen)
+  : DOMEventTargetHelper(aWindow), mScreen(aScreen)
+{
+  MOZ_ASSERT(aWindow);
+  MOZ_ASSERT(aScreen);
+
+  hal::RegisterScreenConfigurationObserver(this);
+
+  hal::ScreenConfiguration config;
+  hal::GetCurrentScreenConfiguration(&config);
+  mType = InternalOrientationToType(config.orientation());
+  mAngle = config.angle();
+
+  nsIDocument* doc = GetResponsibleDocument();
+  if (doc) {
+    doc->SetCurrentOrientation(mType, mAngle);
+  }
+}
+
+ScreenOrientation::~ScreenOrientation()
+{
+  hal::UnregisterScreenConfigurationObserver(this);
+  MOZ_ASSERT(!mFullScreenListener);
+}
+
+class ScreenOrientation::FullScreenEventListener final : public nsIDOMEventListener
+{
+  ~FullScreenEventListener() {}
+public:
+  FullScreenEventListener() {}
+
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIDOMEVENTLISTENER
+};
+
+class ScreenOrientation::VisibleEventListener final : public nsIDOMEventListener
+{
+  ~VisibleEventListener() {}
+public:
+  VisibleEventListener() {}
+
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIDOMEVENTLISTENER
+};
+
+class ScreenOrientation::LockOrientationTask final : public nsIRunnable
+{
+  ~LockOrientationTask();
+public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIRUNNABLE
+
+  LockOrientationTask(ScreenOrientation* aScreenOrientation,
+                      Promise* aPromise,
+                      ScreenOrientationInternal aOrientationLock,
+                      nsIDocument* aDocument,
+                      bool aIsFullScreen);
+protected:
+  bool OrientationLockContains(OrientationType aOrientationType);
+
+  nsRefPtr<ScreenOrientation> mScreenOrientation;
+  nsRefPtr<Promise> mPromise;
+  ScreenOrientationInternal mOrientationLock;
+  nsCOMPtr<nsIDocument> mDocument;
+  bool mIsFullScreen;
+};
+
+NS_IMPL_ISUPPORTS(ScreenOrientation::LockOrientationTask, nsIRunnable)
+
+ScreenOrientation::LockOrientationTask::LockOrientationTask(
+  ScreenOrientation* aScreenOrientation, Promise* aPromise,
+  ScreenOrientationInternal aOrientationLock,
+  nsIDocument* aDocument, bool aIsFullScreen)
+  : mScreenOrientation(aScreenOrientation), mPromise(aPromise),
+    mOrientationLock(aOrientationLock), mDocument(aDocument),
+    mIsFullScreen(aIsFullScreen)
+{
+  MOZ_ASSERT(aScreenOrientation);
+  MOZ_ASSERT(aPromise);
+  MOZ_ASSERT(aDocument);
+}
+
+ScreenOrientation::LockOrientationTask::~LockOrientationTask()
+{
+}
+
+bool
+ScreenOrientation::LockOrientationTask::OrientationLockContains(
+  OrientationType aOrientationType)
+{
+  return mOrientationLock & OrientationTypeToInternal(aOrientationType);
+}
+
+NS_IMETHODIMP
+ScreenOrientation::LockOrientationTask::Run()
+{
+  // Step to lock the orientation as defined in the spec.
+
+  if (mDocument->GetOrientationPendingPromise() != mPromise) {
+    // The document's pending promise is not associated with this task
+    // to lock orientation. There has since been another request to
+    // lock orientation, thus we don't need to do anything. Old promise
+    // should be been rejected.
+    return NS_OK;
+  }
+
+  if (mDocument->Hidden()) {
+    // Active orientation lock is not the document's orientation lock.
+    mPromise->MaybeResolve(JS::UndefinedHandleValue);
+    mDocument->SetOrientationPendingPromise(nullptr);
+    return NS_OK;
+  }
+
+  if (mOrientationLock == eScreenOrientation_None) {
+    mScreenOrientation->UnlockDeviceOrientation();
+    mPromise->MaybeResolve(JS::UndefinedHandleValue);
+    mDocument->SetOrientationPendingPromise(nullptr);
+    return NS_OK;
+  }
+
+  ErrorResult rv;
+  bool result = mScreenOrientation->LockDeviceOrientation(mOrientationLock,
+                                                          mIsFullScreen, rv);
+  if (NS_WARN_IF(rv.Failed())) {
+    return rv.StealNSResult();
+  }
+
+  if (NS_WARN_IF(!result)) {
+    mPromise->MaybeReject(NS_ERROR_UNEXPECTED);
+    mDocument->SetOrientationPendingPromise(nullptr);
+    return NS_OK;
+  }
+
+  if (OrientationLockContains(mDocument->CurrentOrientationType()) ||
+      (mOrientationLock == eScreenOrientation_Default &&
+       mDocument->CurrentOrientationAngle() == 0)) {
+    // Orientation lock will not cause an orientation change.
+    mPromise->MaybeResolve(JS::UndefinedHandleValue);
+    mDocument->SetOrientationPendingPromise(nullptr);
+  }
+
+  return NS_OK;
+}
+
+already_AddRefed<Promise>
+ScreenOrientation::Lock(OrientationLockType aOrientation, ErrorResult& aRv)
+{
+  ScreenOrientationInternal orientation = eScreenOrientation_None;
+
+  switch (aOrientation) {
+  case OrientationLockType::Any:
+    orientation = eScreenOrientation_PortraitPrimary |
+                  eScreenOrientation_PortraitSecondary |
+                  eScreenOrientation_LandscapePrimary |
+                  eScreenOrientation_LandscapeSecondary;
+    break;
+  case OrientationLockType::Natural:
+    orientation |= eScreenOrientation_Default;
+    break;
+  case OrientationLockType::Landscape:
+    orientation = eScreenOrientation_LandscapePrimary |
+                  eScreenOrientation_LandscapeSecondary;
+    break;
+  case OrientationLockType::Portrait:
+    orientation = eScreenOrientation_PortraitPrimary |
+                  eScreenOrientation_PortraitSecondary;
+    break;
+  case OrientationLockType::Portrait_primary:
+    orientation = eScreenOrientation_PortraitPrimary;
+    break;
+  case OrientationLockType::Portrait_secondary:
+    orientation = eScreenOrientation_PortraitSecondary;
+    break;
+  case OrientationLockType::Landscape_primary:
+    orientation = eScreenOrientation_LandscapePrimary;
+    break;
+  case OrientationLockType::Landscape_secondary:
+    orientation = eScreenOrientation_LandscapeSecondary;
+    break;
+  default:
+    NS_WARNING("Unexpected orientation type");
+    aRv.Throw(NS_ERROR_UNEXPECTED);
+    return nullptr;
+  }
+
+  return LockInternal(orientation, aRv);
+}
+
+static inline void
+AbortOrientationPromises(nsIDocShell* aDocShell)
+{
+  MOZ_ASSERT(aDocShell);
+
+  nsIDocument* doc = aDocShell->GetDocument();
+  if (doc) {
+    Promise* promise = doc->GetOrientationPendingPromise();
+    if (promise) {
+      promise->MaybeReject(NS_ERROR_DOM_ABORT_ERR);
+      doc->SetOrientationPendingPromise(nullptr);
+    }
+  }
+
+  int32_t childCount;
+  aDocShell->GetChildCount(&childCount);
+  for (int32_t i = 0; i < childCount; i++) {
+    nsCOMPtr<nsIDocShellTreeItem> child;
+    if (NS_SUCCEEDED(aDocShell->GetChildAt(i, getter_AddRefs(child)))) {
+      nsCOMPtr<nsIDocShell> childShell(do_QueryInterface(child));
+      if (childShell) {
+        AbortOrientationPromises(childShell);
+      }
+    }
+  }
+}
+
+already_AddRefed<Promise>
+ScreenOrientation::LockInternal(ScreenOrientationInternal aOrientation, ErrorResult& aRv)
+{
+  // Steps to apply an orientation lock as defined in spec.
+
+  nsIDocument* doc = GetResponsibleDocument();
+  if (NS_WARN_IF(!doc)) {
+    aRv.Throw(NS_ERROR_UNEXPECTED);
+    return nullptr;
+  }
+
+  nsCOMPtr<nsPIDOMWindow> owner = GetOwner();
+  if (NS_WARN_IF(!owner)) {
+    aRv.Throw(NS_ERROR_UNEXPECTED);
+    return nullptr;
+  }
+
+  nsCOMPtr<nsIDocShell> docShell = owner->GetDocShell();
+  if (NS_WARN_IF(!docShell)) {
+    aRv.Throw(NS_ERROR_UNEXPECTED);
+    return nullptr;
+  }
+
+  nsCOMPtr<nsIGlobalObject> go = do_QueryInterface(owner);
+  MOZ_ASSERT(go);
+  nsRefPtr<Promise> p = Promise::Create(go, aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+#if !defined(MOZ_WIDGET_ANDROID) && !defined(MOZ_WIDGET_GONK)
+  // User agent does not support locking the screen orientation.
+  p->MaybeReject(NS_ERROR_DOM_NOT_SUPPORTED_ERR);
+  return p.forget();
+#else
+  LockPermission perm = GetLockOrientationPermission(true);
+  if (perm == LOCK_DENIED) {
+    p->MaybeReject(NS_ERROR_DOM_SECURITY_ERR);
+    return p.forget();
+  }
+
+  nsCOMPtr<nsIDocShellTreeItem> root;
+  docShell->GetSameTypeRootTreeItem(getter_AddRefs(root));
+  nsCOMPtr<nsIDocShell> rootShell(do_QueryInterface(root));
+  if (!rootShell) {
+    aRv.Throw(NS_ERROR_UNEXPECTED);
+    return nullptr;
+  }
+
+  rootShell->SetOrientationLock(aOrientation);
+  AbortOrientationPromises(rootShell);
+
+  doc->SetOrientationPendingPromise(p);
+
+  nsCOMPtr<nsIRunnable> lockOrientationTask =
+    new LockOrientationTask(this, p, aOrientation, doc,
+                            perm == FULLSCREEN_LOCK_ALLOWED);
+  aRv = NS_DispatchToMainThread(lockOrientationTask);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  return p.forget();
+#endif
+}
+
+bool
+ScreenOrientation::LockDeviceOrientation(ScreenOrientationInternal aOrientation,
+                                         bool aIsFullScreen, ErrorResult& aRv)
+{
+  nsCOMPtr<EventTarget> target = do_QueryInterface(GetOwner()->GetDoc());
+  // We need to register a listener so we learn when we leave full-screen
+  // and when we will have to unlock the screen.
+  // This needs to be done before LockScreenOrientation call to make sure
+  // the locking can be unlocked.
+  if (aIsFullScreen && !target) {
+    return false;
+  }
+
+  if (NS_WARN_IF(!hal::LockScreenOrientation(aOrientation))) {
+    return false;
+  }
+
+  // We are fullscreen and lock has been accepted.
+  if (aIsFullScreen && !mFullScreenListener) {
+    mFullScreenListener = new FullScreenEventListener();
+    aRv = target->AddSystemEventListener(NS_LITERAL_STRING("mozfullscreenchange"),
+                                         mFullScreenListener, /* useCapture = */ true);
+    if (NS_WARN_IF(aRv.Failed())) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+void
+ScreenOrientation::Unlock(ErrorResult& aRv)
+{
+  nsRefPtr<Promise> p = LockInternal(eScreenOrientation_None, aRv);
+}
+
+void
+ScreenOrientation::UnlockDeviceOrientation()
+{
+  hal::UnlockScreenOrientation();
+
+  if (!mFullScreenListener) {
+    return;
+  }
+
+  // Remove event listener in case of fullscreen lock.
+  nsCOMPtr<EventTarget> target = do_QueryInterface(GetOwner()->GetDoc());
+  if (target) {
+    nsresult rv = target->RemoveSystemEventListener(NS_LITERAL_STRING("mozfullscreenchange"),
+                                                    mFullScreenListener, /* useCapture */ true);
+    NS_WARN_IF(NS_FAILED(rv));
+  }
+
+  mFullScreenListener = nullptr;
+}
+
+OrientationType
+ScreenOrientation::DeviceType() const
+{
+  return mType;
+}
+
+uint16_t
+ScreenOrientation::DeviceAngle() const
+{
+  return mAngle;
+}
+
+OrientationType
+ScreenOrientation::GetType(ErrorResult& aRv) const
+{
+  nsIDocument* doc = GetResponsibleDocument();
+  if (!doc) {
+    aRv.Throw(NS_ERROR_UNEXPECTED);
+    return OrientationType::Portrait_primary;
+  }
+
+  return doc->CurrentOrientationType();
+}
+
+uint16_t
+ScreenOrientation::GetAngle(ErrorResult& aRv) const
+{
+  nsIDocument* doc = GetResponsibleDocument();
+  if (!doc) {
+    aRv.Throw(NS_ERROR_UNEXPECTED);
+    return 0;
+  }
+
+  return doc->CurrentOrientationAngle();
+}
+
+ScreenOrientation::LockPermission
+ScreenOrientation::GetLockOrientationPermission(bool aCheckSandbox) const
+{
+  nsCOMPtr<nsPIDOMWindow> owner = GetOwner();
+  if (!owner) {
+    return LOCK_DENIED;
+  }
+
+  // Chrome can always lock the screen orientation.
+  nsIDocShell* docShell = owner->GetDocShell();
+  if (docShell && docShell->ItemType() == nsIDocShellTreeItem::typeChrome) {
+    return LOCK_ALLOWED;
+  }
+
+  nsCOMPtr<nsIDocument> doc = owner->GetDoc();
+  if (!doc || doc->Hidden()) {
+    return LOCK_DENIED;
+  }
+
+  // Sandboxed without "allow-orientation-lock"
+  if (aCheckSandbox && doc->GetSandboxFlags() & SANDBOXED_ORIENTATION_LOCK) {
+    return LOCK_DENIED;
+  }
+
+  // Apps can always lock the screen orientation.
+  if (doc->NodePrincipal()->GetAppStatus() >=
+        nsIPrincipal::APP_STATUS_INSTALLED) {
+    return LOCK_ALLOWED;
+  }
+
+  if (Preferences::GetBool("dom.screenorientation.testing.non_fullscreen_lock_allow",
+                           false)) {
+    return LOCK_ALLOWED;
+  }
+
+  // Other content must be full-screen in order to lock orientation.
+  return doc->MozFullScreen() ? FULLSCREEN_LOCK_ALLOWED : LOCK_DENIED;
+}
+
+nsIDocument*
+ScreenOrientation::GetResponsibleDocument() const
+{
+  nsCOMPtr<nsPIDOMWindow> owner = GetOwner();
+  if (!owner) {
+    return nullptr;
+  }
+
+  return owner->GetDoc();
+}
+
+void
+ScreenOrientation::Notify(const hal::ScreenConfiguration& aConfiguration)
+{
+  nsIDocument* doc = GetResponsibleDocument();
+  if (!doc) {
+    return;
+  }
+
+  ScreenOrientationInternal orientation = aConfiguration.orientation();
+  if (orientation != eScreenOrientation_PortraitPrimary &&
+      orientation != eScreenOrientation_PortraitSecondary &&
+      orientation != eScreenOrientation_LandscapePrimary &&
+      orientation != eScreenOrientation_LandscapeSecondary) {
+    // The platform may notify of some other values from
+    // an orientation lock, but we only care about real
+    // changes to screen orientation which result in one of
+    // the values we care about.
+    return;
+  }
+
+  OrientationType previousOrientation = mType;
+  mAngle = aConfiguration.angle();
+  mType = InternalOrientationToType(orientation);
+
+  nsresult rv;
+  if (mScreen && mType != previousOrientation) {
+    // Use of mozorientationchange is deprecated.
+    rv = mScreen->DispatchTrustedEvent(NS_LITERAL_STRING("mozorientationchange"));
+    NS_WARN_IF(NS_FAILED(rv));
+  }
+
+  if (doc->Hidden() && !mVisibleListener) {
+    mVisibleListener = new VisibleEventListener();
+    rv = doc->AddSystemEventListener(NS_LITERAL_STRING("visibilitychange"),
+                                     mVisibleListener, /* useCapture = */ true);
+    NS_WARN_IF(NS_FAILED(rv));
+    return;
+  }
+
+  if (mType != doc->CurrentOrientationType()) {
+    doc->SetCurrentOrientation(mType, mAngle);
+
+    Promise* pendingPromise = doc->GetOrientationPendingPromise();
+    if (pendingPromise) {
+      pendingPromise->MaybeResolve(JS::UndefinedHandleValue);
+      doc->SetOrientationPendingPromise(nullptr);
+    }
+
+    nsCOMPtr<nsIRunnable> runnable = NS_NewRunnableMethod(this,
+      &ScreenOrientation::DispatchChangeEvent);
+    rv = NS_DispatchToMainThread(runnable);
+    NS_WARN_IF(NS_FAILED(rv));
+  }
+}
+
+void
+ScreenOrientation::UpdateActiveOrientationLock(ScreenOrientationInternal aOrientation)
+{
+  if (aOrientation == eScreenOrientation_None) {
+    hal::UnlockScreenOrientation();
+  } else {
+    hal::LockScreenOrientation(aOrientation);
+  }
+}
+
+void
+ScreenOrientation::DispatchChangeEvent()
+{
+  nsresult rv = DispatchTrustedEvent(NS_LITERAL_STRING("change"));
+  NS_WARN_IF(NS_FAILED(rv));
+}
+
+JSObject*
+ScreenOrientation::WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto)
+{
+  return ScreenOrientationBinding::Wrap(aCx, this, aGivenProto);
+}
+
+NS_IMPL_ISUPPORTS(ScreenOrientation::VisibleEventListener, nsIDOMEventListener)
+
+NS_IMETHODIMP
+ScreenOrientation::VisibleEventListener::HandleEvent(nsIDOMEvent* aEvent)
+{
+  // Document may have become visible, if the page is visible, run the steps
+  // following the "now visible algorithm" as specified.
+  nsCOMPtr<EventTarget> target = aEvent->InternalDOMEvent()->GetCurrentTarget();
+  MOZ_ASSERT(target);
+
+  nsCOMPtr<nsIDocument> doc = do_QueryInterface(target);
+  if (!doc || doc->Hidden()) {
+    return NS_OK;
+  }
+
+  nsGlobalWindow* win = static_cast<nsGlobalWindow*>(doc->GetInnerWindow());
+  if (!win) {
+    return NS_OK;
+  }
+
+  ErrorResult rv;
+  nsScreen* screen = win->GetScreen(rv);
+  if (NS_WARN_IF(rv.Failed())) {
+    return rv.StealNSResult();
+  }
+
+  MOZ_ASSERT(screen);
+  ScreenOrientation* orientation = screen->Orientation();
+  MOZ_ASSERT(orientation);
+
+  rv = target->RemoveSystemEventListener(NS_LITERAL_STRING("visibilitychange"),
+                                         this, true);
+  if (NS_WARN_IF(rv.Failed())) {
+    return rv.StealNSResult();
+  }
+
+  if (doc->CurrentOrientationType() != orientation->DeviceType()) {
+    doc->SetCurrentOrientation(orientation->DeviceType(), orientation->DeviceAngle());
+
+    Promise* pendingPromise = doc->GetOrientationPendingPromise();
+    if (pendingPromise) {
+      pendingPromise->MaybeResolve(JS::UndefinedHandleValue);
+      doc->SetOrientationPendingPromise(nullptr);
+    }
+
+    nsCOMPtr<nsIRunnable> runnable = NS_NewRunnableMethod(orientation,
+      &ScreenOrientation::DispatchChangeEvent);
+    rv = NS_DispatchToMainThread(runnable);
+    if (NS_WARN_IF(rv.Failed())) {
+      return rv.StealNSResult();
+    }
+  }
+
+  return NS_OK;
+}
+
+NS_IMPL_ISUPPORTS(ScreenOrientation::FullScreenEventListener, nsIDOMEventListener)
+
+NS_IMETHODIMP
+ScreenOrientation::FullScreenEventListener::HandleEvent(nsIDOMEvent* aEvent)
+{
+#ifdef DEBUG
+  nsAutoString eventType;
+  aEvent->GetType(eventType);
+
+  MOZ_ASSERT(eventType.EqualsLiteral("mozfullscreenchange"));
+#endif
+
+  nsCOMPtr<EventTarget> target = aEvent->InternalDOMEvent()->GetCurrentTarget();
+  MOZ_ASSERT(target);
+
+  nsCOMPtr<nsIDocument> doc = do_QueryInterface(target);
+  MOZ_ASSERT(doc);
+
+  // We have to make sure that the event we got is the event sent when
+  // fullscreen is disabled because we could get one when fullscreen
+  // got enabled if the lock call is done at the same moment.
+  if (doc->MozFullScreen()) {
+    return NS_OK;
+  }
+
+  hal::UnlockScreenOrientation();
+
+  nsresult rv = target->RemoveSystemEventListener(NS_LITERAL_STRING("mozfullscreenchange"),
+                                                  this, true);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return NS_OK;
+}
diff --git a/dom/base/ScreenOrientation.h b/dom/base/ScreenOrientation.h
index ca2cdca5b1..796cb9a9bd 100644
--- a/dom/base/ScreenOrientation.h
+++ b/dom/base/ScreenOrientation.h
@@ -7,9 +7,16 @@
 #ifndef mozilla_dom_ScreenOrientation_h
 #define mozilla_dom_ScreenOrientation_h
 
+#include "mozilla/DOMEventTargetHelper.h"
+#include "mozilla/dom/ScreenOrientationBinding.h"
+#include "mozilla/HalScreenConfiguration.h"
+
+class nsScreen;
+
 namespace mozilla {
 namespace dom {
 
+class Promise;
 // Make sure that any change to ScreenOrientationInternal values are
 // also made in mobile/android/base/GeckoScreenOrientation.java
 typedef uint32_t ScreenOrientationInternal;
@@ -23,6 +30,90 @@ static const ScreenOrientationInternal eScreenOrientation_LandscapeSecondary = 1
 //it could be PortraitPrimary or LandscapePrimary depends on display resolution
 static const ScreenOrientationInternal eScreenOrientation_Default            = 1u << 4;
 
+class ScreenOrientation final : public DOMEventTargetHelper,
+                                public mozilla::hal::ScreenConfigurationObserver
+{
+  // nsScreen has deprecated API that shares implementation.
+  friend class ::nsScreen;
+
+public:
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(ScreenOrientation, mozilla::DOMEventTargetHelper)
+  NS_REALLY_FORWARD_NSIDOMEVENTTARGET(mozilla::DOMEventTargetHelper)
+
+  IMPL_EVENT_HANDLER(change)
+
+  ScreenOrientation(nsPIDOMWindow* aWindow, nsScreen* aScreen);
+
+  already_AddRefed<Promise> Lock(OrientationLockType aOrientation,
+                                 ErrorResult& aRv);
+
+  void Unlock(ErrorResult& aRv);
+
+  // DeviceType and DeviceAngle gets the current type and angle of the device.
+  OrientationType DeviceType() const;
+  uint16_t DeviceAngle() const;
+
+  // GetType and GetAngle gets the type and angle of the responsible document
+  // (as defined in specification).
+  OrientationType GetType(ErrorResult& aRv) const;
+  uint16_t GetAngle(ErrorResult& aRv) const;
+
+  virtual JSObject* WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto) override;
+
+  void Notify(const mozilla::hal::ScreenConfiguration& aConfiguration) override;
+
+  static void UpdateActiveOrientationLock(ScreenOrientationInternal aOrientation);
+
+private:
+  virtual ~ScreenOrientation();
+
+  // Listener to unlock orientation if we leave fullscreen.
+  class FullScreenEventListener;
+
+  // Listener to update document's orienation lock when document becomes
+  // visible.
+  class VisibleEventListener;
+
+  // Task to run step to lock orientation as defined in specification.
+  class LockOrientationTask;
+
+  enum LockPermission {
+    LOCK_DENIED,
+    FULLSCREEN_LOCK_ALLOWED,
+    LOCK_ALLOWED
+  };
+
+  // This method calls into the HAL to lock the device and sets
+  // up listeners for full screen change.
+  bool LockDeviceOrientation(ScreenOrientationInternal aOrientation,
+                             bool aIsFullscreen, ErrorResult& aRv);
+
+  // This method calls in to the HAL to unlock the device and removes
+  // full screen change listener.
+  void UnlockDeviceOrientation();
+
+  // This method performs the same function as |Lock| except it takes
+  // a ScreenOrientationInternal argument instead of an OrientationType.
+  // This method exists in order to share implementation with nsScreen that
+  // uses ScreenOrientationInternal.
+  already_AddRefed<Promise> LockInternal(ScreenOrientationInternal aOrientation,
+                                         ErrorResult& aRv);
+
+  void DispatchChangeEvent();
+
+  LockPermission GetLockOrientationPermission(bool aCheckSandbox) const;
+
+  // Gets the responsible document as defined in the spec.
+  nsIDocument* GetResponsibleDocument() const;
+
+  nsRefPtr<nsScreen> mScreen;
+  nsRefPtr<FullScreenEventListener> mFullScreenListener;
+  nsRefPtr<VisibleEventListener> mVisibleListener;
+  OrientationType mType;
+  uint16_t mAngle;
+};
+
 } // namespace dom
 } // namespace mozilla
 
diff --git a/dom/base/StructuredCloneHelper.cpp b/dom/base/StructuredCloneHelper.cpp
index 20583cbee5..1ba82f186d 100644
--- a/dom/base/StructuredCloneHelper.cpp
+++ b/dom/base/StructuredCloneHelper.cpp
@@ -7,11 +7,18 @@
 #include "StructuredCloneHelper.h"
 
 #include "ImageContainer.h"
+#include "mozilla/AutoRestore.h"
 #include "mozilla/dom/BlobBinding.h"
+#include "mozilla/dom/File.h"
+#include "mozilla/dom/FileList.h"
 #include "mozilla/dom/FileListBinding.h"
 #include "mozilla/dom/ImageBitmap.h"
 #include "mozilla/dom/ImageBitmapBinding.h"
+#include "mozilla/dom/MessagePort.h"
+#include "mozilla/dom/MessagePortBinding.h"
+#include "mozilla/dom/PMessagePort.h"
 #include "mozilla/dom/StructuredCloneTags.h"
+#include "mozilla/dom/ToJSValue.h"
 
 namespace mozilla {
 namespace dom {
diff --git a/dom/base/StructuredCloneHelper.h b/dom/base/StructuredCloneHelper.h
index b8e97e99df..0c72104e66 100644
--- a/dom/base/StructuredCloneHelper.h
+++ b/dom/base/StructuredCloneHelper.h
@@ -12,6 +12,7 @@
 #include "nsTArray.h"
 
 namespace mozilla {
+class ErrorResult;
 namespace layers {
 class Image;
 }
diff --git a/dom/base/moz.build b/dom/base/moz.build
index 2925843e6f..7d084d2168 100644
--- a/dom/base/moz.build
+++ b/dom/base/moz.build
@@ -333,6 +333,7 @@ UNIFIED_SOURCES += [
     'ProcessGlobal.cpp',
     'ResponsiveImageSelector.cpp',
     'SameProcessMessageQueue.cpp',
+    'ScreenOrientation.cpp',
     'ScriptSettings.cpp',
     'ShadowRoot.cpp',
     'StructuredCloneHelper.cpp',
diff --git a/dom/base/nsAttrValue.h b/dom/base/nsAttrValue.h
index 66c1b0c47f..c1dee8b7a1 100644
--- a/dom/base/nsAttrValue.h
+++ b/dom/base/nsAttrValue.h
@@ -25,6 +25,9 @@
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/dom/BindingDeclarations.h"
 
+// Undefine LoadImage to prevent naming conflict with Windows.
+#undef LoadImage
+
 class nsAString;
 class nsIDocument;
 class nsStyledElementNotElementCSSInlineStyle;
diff --git a/dom/base/nsContentUtils.cpp b/dom/base/nsContentUtils.cpp
index 70549e7442..7ddfde0aac 100644
--- a/dom/base/nsContentUtils.cpp
+++ b/dom/base/nsContentUtils.cpp
@@ -1341,6 +1341,7 @@ nsContentUtils::ParseSandboxAttributeToFlags(const nsAttrValue* sandboxAttr)
                | SANDBOXED_SCRIPTS
                | SANDBOXED_AUTOMATIC_FEATURES
                | SANDBOXED_POINTER_LOCK
+               | SANDBOXED_ORIENTATION_LOCK
                | SANDBOXED_DOMAIN;
 
 // Macro for updating the flag according to the keywords
@@ -1352,6 +1353,7 @@ nsContentUtils::ParseSandboxAttributeToFlags(const nsAttrValue* sandboxAttr)
   IF_KEYWORD(allowscripts, SANDBOXED_SCRIPTS | SANDBOXED_AUTOMATIC_FEATURES)
   IF_KEYWORD(allowtopnavigation, SANDBOXED_TOPLEVEL_NAVIGATION)
   IF_KEYWORD(allowpointerlock, SANDBOXED_POINTER_LOCK)
+  IF_KEYWORD(alloworientationlock, SANDBOXED_ORIENTATION_LOCK)
   IF_KEYWORD(allowpopups, SANDBOXED_AUXILIARY_NAVIGATION)
 
   return out;
diff --git a/dom/base/nsDocument.cpp b/dom/base/nsDocument.cpp
index 1d54f18908..70024fb526 100644
--- a/dom/base/nsDocument.cpp
+++ b/dom/base/nsDocument.cpp
@@ -38,6 +38,7 @@
 #include "nsQueryObject.h"
 #include "nsDOMClassInfo.h"
 #include "mozilla/Services.h"
+#include "nsScreen.h"
 
 #include "mozilla/AsyncEventDispatcher.h"
 #include "mozilla/BasicEvents.h"
@@ -1922,6 +1923,7 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INTERNAL(nsDocument)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mFirstBaseNodeWithHref)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mDOMImplementation)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mImageMaps)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mOrientationPendingPromise)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mOriginalDocument)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mCachedEncoder)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mStateObjectCached)
@@ -2022,6 +2024,7 @@ NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(nsDocument)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mChildrenCollection)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mRegistry)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mMasterDocument)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mOrientationPendingPromise)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mImportManager)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mSubImportLinks)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mFontFaceSet)
@@ -12032,6 +12035,38 @@ nsDocument::IsFullScreenEnabled(bool aCallerIsChrome, bool aLogFailure)
   return allowed;
 }
 
+uint16_t
+nsDocument::CurrentOrientationAngle() const
+{
+  return mCurrentOrientationAngle;
+}
+
+OrientationType
+nsDocument::CurrentOrientationType() const
+{
+  return mCurrentOrientationType;
+}
+
+void
+nsDocument::SetCurrentOrientation(mozilla::dom::OrientationType aType,
+                                  uint16_t aAngle)
+{
+  mCurrentOrientationType = aType;
+  mCurrentOrientationAngle = aAngle;
+}
+
+Promise*
+nsDocument::GetOrientationPendingPromise() const
+{
+  return mOrientationPendingPromise;
+}
+
+void
+nsDocument::SetOrientationPendingPromise(Promise* aPromise)
+{
+  mOrientationPendingPromise = aPromise;
+}
+
 static void
 DispatchPointerLockChange(nsIDocument* aTarget)
 {
diff --git a/dom/base/nsDocument.h b/dom/base/nsDocument.h
index ca02523b06..4bd77b27d3 100644
--- a/dom/base/nsDocument.h
+++ b/dom/base/nsDocument.h
@@ -1273,6 +1273,13 @@ public:
   bool SetPointerLock(Element* aElement, int aCursorStyle);
   static void UnlockPointer(nsIDocument* aDoc = nullptr);
 
+  void SetCurrentOrientation(mozilla::dom::OrientationType aType,
+                             uint16_t aAngle) override;
+  uint16_t CurrentOrientationAngle() const override;
+  mozilla::dom::OrientationType CurrentOrientationType() const override;
+  void SetOrientationPendingPromise(mozilla::dom::Promise* aPromise) override;
+  mozilla::dom::Promise* GetOrientationPendingPromise() const override;
+
   // This method may fire a DOM event; if it does so it will happen
   // synchronously.
   void UpdateVisibilityState();
@@ -1510,6 +1517,8 @@ protected:
   virtual nsIScriptGlobalObject* GetScriptHandlingObjectInternal() const override;
   virtual bool InternalAllowXULXBL() override;
 
+  void UpdateScreenOrientation();
+
 #define NS_DOCUMENT_NOTIFY_OBSERVERS(func_, params_)                        \
   NS_OBSERVER_ARRAY_NOTIFY_XPCOM_OBSERVERS(mObservers, nsIDocumentObserver, \
                                            func_, params_);
@@ -1674,6 +1683,13 @@ public:
 
   bool mAsyncFullscreenPending:1;
 
+  // ScreenOrientation "pending promise" as described by
+  // http://www.w3.org/TR/screen-orientation/
+  nsRefPtr<mozilla::dom::Promise> mOrientationPendingPromise;
+
+  uint16_t mCurrentOrientationAngle;
+  mozilla::dom::OrientationType mCurrentOrientationType;
+
   // Whether we're observing the "app-theme-changed" observer service
   // notification.  We need to keep track of this because we might get multiple
   // OnPageShow notifications in a row without an OnPageHide in between, if
diff --git a/dom/base/nsGkAtomList.h b/dom/base/nsGkAtomList.h
index d018a60709..bbe3930262 100644
--- a/dom/base/nsGkAtomList.h
+++ b/dom/base/nsGkAtomList.h
@@ -79,6 +79,7 @@ GK_ATOM(allowevents, "allowevents")
 GK_ATOM(allownegativeassertions, "allownegativeassertions")
 GK_ATOM(allowforms,"allow-forms")
 GK_ATOM(allowfullscreen, "allowfullscreen")
+GK_ATOM(alloworientationlock,"allow-orientation-lock")
 GK_ATOM(allowpointerlock,"allow-pointer-lock")
 GK_ATOM(allowpopups,"allow-popups")
 GK_ATOM(allowsameorigin,"allow-same-origin")
diff --git a/dom/base/nsIDocument.h b/dom/base/nsIDocument.h
index b28c6dde38..a1e03e05c1 100644
--- a/dom/base/nsIDocument.h
+++ b/dom/base/nsIDocument.h
@@ -132,7 +132,9 @@ class MediaQueryList;
 class GlobalObject;
 class NodeFilter;
 class NodeIterator;
+enum class OrientationType : uint32_t;
 class ProcessingInstruction;
+class Promise;
 class Selection;
 class StyleSheetList;
 class SVGDocument;
@@ -1204,6 +1206,14 @@ public:
 
   static void UnlockPointer(nsIDocument* aDoc = nullptr);
 
+  // ScreenOrientation related APIs
+
+  virtual void SetCurrentOrientation(mozilla::dom::OrientationType aType,
+                                     uint16_t aAngle) = 0;
+  virtual uint16_t CurrentOrientationAngle() const = 0;
+  virtual mozilla::dom::OrientationType CurrentOrientationType() const = 0;
+  virtual void SetOrientationPendingPromise(mozilla::dom::Promise* aPromise) = 0;
+  virtual mozilla::dom::Promise* GetOrientationPendingPromise() const = 0;
 
   //----------------------------------------------------------------------
 
diff --git a/dom/base/nsSandboxFlags.h b/dom/base/nsSandboxFlags.h
index 2725ce4baa..0435db5f61 100644
--- a/dom/base/nsSandboxFlags.h
+++ b/dom/base/nsSandboxFlags.h
@@ -76,4 +76,9 @@ const unsigned long SANDBOXED_DOMAIN = 0x100;
  * showModalDialog() method.
  */
 const unsigned long SANDBOXED_AUXILIARY_NAVIGATION = 0x200;
+
+/**
+ * This flag prevents locking screen orientation.
+ */
+const unsigned long SANDBOXED_ORIENTATION_LOCK = 0x400;
 #endif
diff --git a/dom/base/nsScreen.cpp b/dom/base/nsScreen.cpp
index 0cbba5c5be..06d86d4753 100644
--- a/dom/base/nsScreen.cpp
+++ b/dom/base/nsScreen.cpp
@@ -4,7 +4,6 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-#include "mozilla/Hal.h"
 #include "mozilla/dom/Event.h" // for nsIDOMEvent::InternalDOMEvent()
 #include "mozilla/dom/ScreenBinding.h"
 #include "nsScreen.h"
@@ -36,36 +35,32 @@ nsScreen::Create(nsPIDOMWindow* aWindow)
   NS_ENSURE_TRUE(sgo, nullptr);
 
   nsRefPtr<nsScreen> screen = new nsScreen(aWindow);
-
-  hal::RegisterScreenConfigurationObserver(screen);
-  hal::ScreenConfiguration config;
-  hal::GetCurrentScreenConfiguration(&config);
-  screen->mOrientationInternal = config.orientation();
-
   return screen.forget();
 }
 
 nsScreen::nsScreen(nsPIDOMWindow* aWindow)
   : DOMEventTargetHelper(aWindow)
-  , mEventListener(nullptr)
+  , mScreenOrientation(new ScreenOrientation(aWindow, this))
 {
 }
 
 nsScreen::~nsScreen()
 {
-  MOZ_ASSERT(!mEventListener);
-  hal::UnregisterScreenConfigurationObserver(this);
 }
 
 
 // QueryInterface implementation for nsScreen
-NS_INTERFACE_MAP_BEGIN(nsScreen)
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION_INHERITED(nsScreen)
   NS_INTERFACE_MAP_ENTRY(nsIDOMScreen)
 NS_INTERFACE_MAP_END_INHERITING(DOMEventTargetHelper)
 
 NS_IMPL_ADDREF_INHERITED(nsScreen, DOMEventTargetHelper)
 NS_IMPL_RELEASE_INHERITED(nsScreen, DOMEventTargetHelper)
 
+NS_IMPL_CYCLE_COLLECTION_INHERITED(nsScreen,
+                                   DOMEventTargetHelper,
+                                   mScreenOrientation)
+
 int32_t
 nsScreen::GetPixelDepth(ErrorResult& aRv)
 {
@@ -162,45 +157,33 @@ nsScreen::GetAvailRect(nsRect& aRect)
   return NS_OK;
 }
 
-void
-nsScreen::Notify(const hal::ScreenConfiguration& aConfiguration)
+mozilla::dom::ScreenOrientation*
+nsScreen::Orientation() const
 {
-  ScreenOrientationInternal previousOrientation = mOrientationInternal;
-  mOrientationInternal = aConfiguration.orientation();
-
-  NS_ASSERTION(mOrientationInternal == eScreenOrientation_PortraitPrimary ||
-               mOrientationInternal == eScreenOrientation_PortraitSecondary ||
-               mOrientationInternal == eScreenOrientation_LandscapePrimary ||
-               mOrientationInternal == eScreenOrientation_LandscapeSecondary,
-               "Invalid orientation value passed to notify method!");
-
-  if (mOrientationInternal != previousOrientation) {
-    DispatchTrustedEvent(NS_LITERAL_STRING("mozorientationchange"));
-  }
+  return mScreenOrientation;
 }
 
 void
-nsScreen::GetMozOrientation(nsString& aOrientation)
+nsScreen::GetMozOrientation(nsString& aOrientation) const
 {
   if (ShouldResistFingerprinting()) {
     aOrientation.AssignLiteral("landscape-primary");
   } else {
-    switch (mOrientationInternal) {
-    case eScreenOrientation_PortraitPrimary:
+    switch (mScreenOrientation->DeviceType()) {
+    case OrientationType::Portrait_primary:
       aOrientation.AssignLiteral("portrait-primary");
       break;
-    case eScreenOrientation_PortraitSecondary:
+    case OrientationType::Portrait_secondary:
       aOrientation.AssignLiteral("portrait-secondary");
       break;
-    case eScreenOrientation_LandscapePrimary:
+    case OrientationType::Landscape_primary:
       aOrientation.AssignLiteral("landscape-primary");
       break;
-    case eScreenOrientation_LandscapeSecondary:
+    case OrientationType::Landscape_secondary:
       aOrientation.AssignLiteral("landscape-secondary");
       break;
-    case eScreenOrientation_None:
     default:
-      MOZ_CRASH("Unacceptable mOrientationInternal value");
+      MOZ_CRASH("Unacceptable screen orientation type.");
     }
   }
 }
@@ -214,35 +197,6 @@ nsScreen::GetSlowMozOrientation(nsAString& aOrientation)
   return NS_OK;
 }
 
-nsScreen::LockPermission
-nsScreen::GetLockOrientationPermission() const
-{
-  nsCOMPtr<nsPIDOMWindow> owner = GetOwner();
-  if (!owner) {
-    return LOCK_DENIED;
-  }
-
-  // Chrome can always lock the screen orientation.
-  nsIDocShell* docShell = owner->GetDocShell();
-  if (docShell && docShell->ItemType() == nsIDocShellTreeItem::typeChrome) {
-    return LOCK_ALLOWED;
-  }
-
-  nsCOMPtr<nsIDocument> doc = owner->GetDoc();
-  if (!doc || doc->Hidden()) {
-    return LOCK_DENIED;
-  }
-
-  // Apps can always lock the screen orientation.
-  if (doc->NodePrincipal()->GetAppStatus() >=
-        nsIPrincipal::APP_STATUS_INSTALLED) {
-    return LOCK_ALLOWED;
-  }
-
-  // Other content must be full-screen in order to lock orientation.
-  return doc->MozFullScreen() ? FULLSCREEN_LOCK_ALLOWED : LOCK_DENIED;
-}
-
 bool
 nsScreen::MozLockOrientation(const nsAString& aOrientation, ErrorResult& aRv)
 {
@@ -287,34 +241,13 @@ nsScreen::MozLockOrientation(const Sequence<nsString>& aOrientations,
     }
   }
 
-  switch (GetLockOrientationPermission()) {
-    case LOCK_DENIED:
+  switch (mScreenOrientation->GetLockOrientationPermission(false)) {
+    case ScreenOrientation::LOCK_DENIED:
       return false;
-    case LOCK_ALLOWED:
-      return hal::LockScreenOrientation(orientation);
-    case FULLSCREEN_LOCK_ALLOWED: {
-      // We need to register a listener so we learn when we leave full-screen
-      // and when we will have to unlock the screen.
-      // This needs to be done before LockScreenOrientation call to make sure
-      // the locking can be unlocked.
-      nsCOMPtr<EventTarget> target = do_QueryInterface(GetOwner()->GetDoc());
-      if (!target) {
-        return false;
-      }
-
-      if (!hal::LockScreenOrientation(orientation)) {
-        return false;
-      }
-
-      // We are fullscreen and lock has been accepted.
-      if (!mEventListener) {
-        mEventListener = new FullScreenEventListener();
-      }
-
-      aRv = target->AddSystemEventListener(NS_LITERAL_STRING("mozfullscreenchange"),
-                                           mEventListener, /* useCapture = */ true);
-      return true;
-    }
+    case ScreenOrientation::LOCK_ALLOWED:
+      return mScreenOrientation->LockDeviceOrientation(orientation, false, aRv);
+    case ScreenOrientation::FULLSCREEN_LOCK_ALLOWED:
+      return mScreenOrientation->LockDeviceOrientation(orientation, true, aRv);
   }
 
   // This is only for compilers that don't understand that the previous switch
@@ -325,20 +258,7 @@ nsScreen::MozLockOrientation(const Sequence<nsString>& aOrientations,
 void
 nsScreen::MozUnlockOrientation()
 {
-  hal::UnlockScreenOrientation();
-
-  if (!mEventListener) {
-    return;
-  }
-
-  // Remove event listener in case of fullscreen lock.
-  nsCOMPtr<EventTarget> target = do_QueryInterface(GetOwner()->GetDoc());
-  if (target) {
-    target->RemoveSystemEventListener(NS_LITERAL_STRING("mozfullscreenchange"),
-                                      mEventListener, /* useCapture */ true);
-  }
-
-  mEventListener = nullptr;
+  mScreenOrientation->UnlockDeviceOrientation();
 }
 
 bool
@@ -361,39 +281,6 @@ nsScreen::WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto)
   return ScreenBinding::Wrap(aCx, this, aGivenProto);
 }
 
-NS_IMPL_ISUPPORTS(nsScreen::FullScreenEventListener, nsIDOMEventListener)
-
-NS_IMETHODIMP
-nsScreen::FullScreenEventListener::HandleEvent(nsIDOMEvent* aEvent)
-{
-#ifdef DEBUG
-  nsAutoString eventType;
-  aEvent->GetType(eventType);
-
-  MOZ_ASSERT(eventType.EqualsLiteral("mozfullscreenchange"));
-#endif
-
-  nsCOMPtr<EventTarget> target = aEvent->InternalDOMEvent()->GetCurrentTarget();
-  MOZ_ASSERT(target);
-
-  nsCOMPtr<nsIDocument> doc = do_QueryInterface(target);
-  MOZ_ASSERT(doc);
-
-  // We have to make sure that the event we got is the event sent when
-  // fullscreen is disabled because we could get one when fullscreen
-  // got enabled if the lock call is done at the same moment.
-  if (doc->MozFullScreen()) {
-    return NS_OK;
-  }
-
-  target->RemoveSystemEventListener(NS_LITERAL_STRING("mozfullscreenchange"),
-                                    this, true);
-
-  hal::UnlockScreenOrientation();
-
-  return NS_OK;
-}
-
 nsresult
 nsScreen::GetWindowInnerRect(nsRect& aRect)
 {
diff --git a/dom/base/nsScreen.h b/dom/base/nsScreen.h
index 9030bb69d8..2041c1c759 100644
--- a/dom/base/nsScreen.h
+++ b/dom/base/nsScreen.h
@@ -10,7 +10,6 @@
 #include "mozilla/dom/ScreenOrientation.h"
 #include "mozilla/DOMEventTargetHelper.h"
 #include "mozilla/ErrorResult.h"
-#include "mozilla/HalScreenConfiguration.h"
 #include "nsIDOMScreen.h"
 #include "nsCOMPtr.h"
 #include "nsRect.h"
@@ -20,7 +19,6 @@ class nsDeviceContext;
 // Script "screen" object
 class nsScreen : public mozilla::DOMEventTargetHelper
                , public nsIDOMScreen
-               , public mozilla::hal::ScreenConfigurationObserver
 {
   typedef mozilla::ErrorResult ErrorResult;
 public:
@@ -28,6 +26,7 @@ public:
 
   NS_DECL_ISUPPORTS_INHERITED
   NS_DECL_NSIDOMSCREEN
+  NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(nsScreen, mozilla::DOMEventTargetHelper)
   NS_REALLY_FORWARD_NSIDOMEVENTTARGET(mozilla::DOMEventTargetHelper)
 
   nsPIDOMWindow* GetParentObject() const
@@ -115,7 +114,8 @@ public:
     return rect.height;
   }
 
-  void GetMozOrientation(nsString& aOrientation);
+  // Deprecated
+  void GetMozOrientation(nsString& aOrientation) const;
 
   IMPL_EVENT_HANDLER(mozorientationchange)
 
@@ -125,7 +125,7 @@ public:
 
   virtual JSObject* WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto) override;
 
-  void Notify(const mozilla::hal::ScreenConfiguration& aConfiguration) override;
+  mozilla::dom::ScreenOrientation* Orientation() const;
 
 protected:
   nsDeviceContext* GetDeviceContext();
@@ -133,35 +133,15 @@ protected:
   nsresult GetAvailRect(nsRect& aRect);
   nsresult GetWindowInnerRect(nsRect& aRect);
 
-  mozilla::dom::ScreenOrientationInternal mOrientationInternal;
-
 private:
-  class FullScreenEventListener final : public nsIDOMEventListener
-  {
-    ~FullScreenEventListener() {}
-  public:
-    FullScreenEventListener() {}
-
-    NS_DECL_ISUPPORTS
-    NS_DECL_NSIDOMEVENTLISTENER
-  };
-
   explicit nsScreen(nsPIDOMWindow* aWindow);
   virtual ~nsScreen();
 
-  enum LockPermission {
-    LOCK_DENIED,
-    FULLSCREEN_LOCK_ALLOWED,
-    LOCK_ALLOWED
-  };
-
-  LockPermission GetLockOrientationPermission() const;
-
   bool IsDeviceSizePageSize();
 
   bool ShouldResistFingerprinting() const;
 
-  nsRefPtr<FullScreenEventListener> mEventListener;
+  nsRefPtr<mozilla::dom::ScreenOrientation> mScreenOrientation;
 };
 
 #endif /* nsScreen_h___ */
diff --git a/dom/base/test/file_lock_orientation.html b/dom/base/test/file_lock_orientation.html
new file mode 100644
index 0000000000..e370ab91c8
--- /dev/null
+++ b/dom/base/test/file_lock_orientation.html
@@ -0,0 +1,14 @@
+<!DOCTYPE html>
+<html>
+<body>
+<script src="orientationcommon.js"></script>
+<script>
+window.addEventListener("message", function(event) {
+  var p = specialPowersLock(event.data);
+  p.then(function() {
+    event.source.postMessage("success", "*");
+  }).catch(function(err) {
+    event.source.postMessage("error", "*");
+  });
+}, false);
+</script>
diff --git a/dom/base/test/file_record_orientation.html b/dom/base/test/file_record_orientation.html
new file mode 100644
index 0000000000..a01587507b
--- /dev/null
+++ b/dom/base/test/file_record_orientation.html
@@ -0,0 +1,16 @@
+<!DOCTYPE html>
+<html>
+<body>
+<script>
+var recordedOrientations = [];
+
+screen.orientation.onchange = function() {
+  recordedOrientations.push(screen.orientation.type);
+};
+
+window.addEventListener("message", function(event) {
+  if (event.data == "report") {
+    event.source.postMessage(recordedOrientations, "*");
+  }
+}, false);
+</script>
diff --git a/dom/base/test/mochitest.ini b/dom/base/test/mochitest.ini
index 1ad4e0921a..db9beff154 100644
--- a/dom/base/test/mochitest.ini
+++ b/dom/base/test/mochitest.ini
@@ -179,11 +179,13 @@ support-files =
   file_htmlserializer_2_latin1.html
   file_htmlserializer_ipv6.html
   file_htmlserializer_ipv6_out.html
+  file_lock_orientation.html
   file_mozfiledataurl_audio.ogg
   file_mozfiledataurl_doc.html
   file_mozfiledataurl_img.jpg
   file_mozfiledataurl_inner.html
   file_mozfiledataurl_text.txt
+  file_record_orientation.html
   file_restrictedEventSource.sjs
   file_simplecontentpolicy.js
   file_websocket_basic_wsh.py
@@ -222,6 +224,7 @@ support-files =
   invalid_accesscontrol.resource
   invalid_accesscontrol.resource^headers^
   mutationobserver_dialog.html
+  orientationcommon.js
   progressserver.sjs
   responseIdentical.sjs
   script-1_bug597345.sjs
@@ -304,6 +307,14 @@ skip-if = (buildapp == 'b2g' && toolkit != 'gonk') # Fails on b2g-desktop, track
 [test_pluginAudioNotification.html]
 skip-if = (buildapp == 'b2g' || buildapp == 'mulet' || toolkit == 'android') # Plugins don't work on Android and/or B2G/Mulet
 [test_screen_orientation.html]
+[test_orientation_alternate.html]
+skip-if = toolkit != 'gonk'
+[test_orientation_frame.html]
+skip-if = toolkit != 'gonk'
+[test_orientation_frame_lock.html]
+skip-if = toolkit != 'gonk'
+[test_orientation_sandbox_no_lock.html]
+skip-if = toolkit != 'gonk'
 [test_settimeout_extra_arguments.html]
 [test_settimeout_inner.html]
 [test_setting_opener.html]
diff --git a/dom/base/test/orientationcommon.js b/dom/base/test/orientationcommon.js
new file mode 100644
index 0000000000..2d87cf7207
--- /dev/null
+++ b/dom/base/test/orientationcommon.js
@@ -0,0 +1,21 @@
+function specialPowersLock(orientation) {
+  return new Promise(function(resolve, reject) {
+    SpecialPowers.pushPrefEnv({
+      'set': [ ["dom.screenorientation.testing.non_fullscreen_lock_allow", true] ]
+    }, function() {
+      var p = screen.orientation.lock(orientation);
+      resolve(p);
+    });
+  });
+}
+
+function specialPowersUnlock() {
+  return new Promise(function(resolve, reject) {
+    SpecialPowers.pushPrefEnv({
+      'set': [ ["dom.screenorientation.testing.non_fullscreen_lock_allow", true] ]
+    }, function() {
+      screen.orientation.unlock();
+      resolve();
+    });
+  });
+}
diff --git a/dom/base/test/test_orientation_alternate.html b/dom/base/test/test_orientation_alternate.html
new file mode 100644
index 0000000000..7276ad82cc
--- /dev/null
+++ b/dom/base/test/test_orientation_alternate.html
@@ -0,0 +1,27 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>Test for ScreenOrientation API</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="orientationcommon.js"></script>
+<div id="log"></div>
+<script>
+async_test(function(t) {
+  var originalOrientation = screen.orientation.type;
+  var alternateOrientation = originalOrientation == "portrait-primary" ?
+    "landscape-primary" : "portrait-primary";
+  var p = specialPowersLock(alternateOrientation);
+  p.then(function() {
+    t.step(function() { assert_equals(screen.orientation.type, alternateOrientation); });
+    return specialPowersLock(originalOrientation);
+  }).then(function() {
+    t.step(function() { assert_equals(screen.orientation.type, originalOrientation); });
+    return specialPowersUnlock();
+  }).then(function() {
+    t.done();
+  }).catch(t.step_func(function(err) {
+    assert_unreached("Error setting orientation: " + err);
+    t.done();
+  }));
+}, "Test locking and unlocking orientation.");
+</script>
diff --git a/dom/base/test/test_orientation_frame.html b/dom/base/test/test_orientation_frame.html
new file mode 100644
index 0000000000..748b3264ea
--- /dev/null
+++ b/dom/base/test/test_orientation_frame.html
@@ -0,0 +1,37 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>Test for ScreenOrientation API</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="orientationcommon.js"></script>
+<div id="log"></div>
+<iframe id="frame"></iframe>
+<script>
+async_test(function(t) {
+  var originalOrientation = screen.orientation.type;
+  var alternateOrientation = originalOrientation == "portrait-primary" ?
+    "landscape-primary" : "portrait-primary";
+
+  window.addEventListener("message", function(event) {
+    t.step(function() { assert_array_equals(event.data, [alternateOrientation, originalOrientation]); });
+    t.done();
+  }, false);
+
+  var frame = document.getElementById("frame");
+  frame.src = "file_record_orientation.html";
+
+  frame.onload = function() {
+    var p = specialPowersLock(alternateOrientation);
+    p.then(function() {
+      return specialPowersLock(originalOrientation);
+    }).then(function() {
+      return specialPowersUnlock();
+    }).then(function() {
+      frame.contentWindow.postMessage("report", "*");
+    }).catch(t.step_func(function(err) {
+      assert_unreached("Error setting orientation: " + err);
+      t.done();
+    }));
+  };
+}, "Test orientation change event in frame.");
+</script>
diff --git a/dom/base/test/test_orientation_frame_lock.html b/dom/base/test/test_orientation_frame_lock.html
new file mode 100644
index 0000000000..f8b7a65d08
--- /dev/null
+++ b/dom/base/test/test_orientation_frame_lock.html
@@ -0,0 +1,46 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>Test for ScreenOrientation API</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="orientationcommon.js"></script>
+<div id="log"></div>
+<iframe sandbox="allow-scripts allow-orientation-lock" id="frame"></iframe>
+<script>
+async_test(function(t) {
+  var originalOrientation = screen.orientation.type;
+  var alternateOrientation = originalOrientation == "portrait-primary" ?
+    "landscape-primary" : "portrait-primary";
+
+  var orientationChanges = [];
+  window.screen.orientation.onchange = function() {
+    orientationChanges.push(screen.orientation.type);
+  };
+
+  window.addEventListener("message", function(event) {
+    t.step(function() {
+      assert_equals(event.data, "success");
+      assert_array_equals(orientationChanges, [ alternateOrientation ]);
+    });
+
+    // Return the orientation to its original settings.
+    var p = specialPowersLock(originalOrientation);
+    p.then(function() {
+      return specialPowersUnlock();
+    }).then(function() {
+      t.done();
+    }).catch(t.step_func(function(err) {
+      assert_unreached("Error setting orientation: " + err);
+      t.done();
+    }));
+  }, false);
+
+  var frame = document.getElementById("frame");
+  frame.src = "http://example.com/tests/dom/base/test/file_lock_orientation.html";
+
+  frame.onload = function() {
+    assert_array_equals(orientationChanges, []);
+    frame.contentWindow.postMessage(alternateOrientation, "*");
+  };
+}, "Test orientation lock from within a frame with sandbox permission.");
+</script>
diff --git a/dom/base/test/test_orientation_sandbox_no_lock.html b/dom/base/test/test_orientation_sandbox_no_lock.html
new file mode 100644
index 0000000000..e020a6daa9
--- /dev/null
+++ b/dom/base/test/test_orientation_sandbox_no_lock.html
@@ -0,0 +1,36 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>Test for ScreenOrientation API</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="orientationcommon.js"></script>
+<div id="log"></div>
+<iframe sandbox="allow-scripts" id="frame"></iframe>
+<script>
+async_test(function(t) {
+  var originalOrientation = screen.orientation.type;
+  var alternateOrientation = originalOrientation == "portrait-primary" ?
+    "landscape-primary" : "portrait-primary";
+
+  var orientationChanges = [];
+  window.screen.orientation.onchange = function() {
+    orientationChanges.push(screen.orientation.type);
+  };
+
+  window.addEventListener("message", function(event) {
+    t.step(function() {
+      assert_equals(event.data, "error");
+      assert_array_equals(orientationChanges, []);
+      t.done();
+    });
+  }, false);
+
+  var frame = document.getElementById("frame");
+  frame.src = "http://example.com/tests/dom/base/test/file_lock_orientation.html";
+
+  frame.onload = function() {
+    assert_array_equals(orientationChanges, []);
+    frame.contentWindow.postMessage(alternateOrientation, "*");
+  };
+}, "Test orientation lock from within a frame without sandbox permission.");
+</script>
diff --git a/dom/canvas/ImageBitmap.h b/dom/canvas/ImageBitmap.h
index 568b46610d..f80f3ce452 100644
--- a/dom/canvas/ImageBitmap.h
+++ b/dom/canvas/ImageBitmap.h
@@ -18,6 +18,8 @@ struct JSContext;
 struct JSStructuredCloneReader;
 struct JSStructuredCloneWriter;
 
+class nsIGlobalObject;
+
 namespace mozilla {
 
 class ErrorResult;
diff --git a/dom/mobilemessage/MobileMessageManager.h b/dom/mobilemessage/MobileMessageManager.h
index 73502930cb..a858490189 100644
--- a/dom/mobilemessage/MobileMessageManager.h
+++ b/dom/mobilemessage/MobileMessageManager.h
@@ -14,11 +14,11 @@
 class nsISmsService;
 class nsIDOMMozSmsMessage;
 class nsIDOMMozMmsMessage;
-class Promise;
 
 namespace mozilla {
 namespace dom {
 
+class Promise;
 class DOMRequest;
 class DOMCursor;
 struct MmsParameters;
diff --git a/dom/tests/mochitest/general/test_interfaces.html b/dom/tests/mochitest/general/test_interfaces.html
index 8bf542377c..f7867241d2 100644
--- a/dom/tests/mochitest/general/test_interfaces.html
+++ b/dom/tests/mochitest/general/test_interfaces.html
@@ -965,6 +965,8 @@ var interfaceNamesInGlobalScope =
     "RTCStatsReport",
 // IMPORTANT: Do not change this list without review from a DOM peer!
     "Screen",
+// IMPORTANT: Do not change this list without review from a DOM peer!
+    "ScreenOrientation",
 // IMPORTANT: Do not change this list without review from a DOM peer!
     "ScriptProcessorNode",
 // IMPORTANT: Do not change this list without review from a DOM peer!
diff --git a/dom/webidl/Screen.webidl b/dom/webidl/Screen.webidl
index ca01103122..6b5824fa88 100644
--- a/dom/webidl/Screen.webidl
+++ b/dom/webidl/Screen.webidl
@@ -29,6 +29,7 @@ interface Screen : EventTarget {
   readonly attribute long availLeft;
 
   /**
+   * DEPRECATED, use ScreenOrientation API instead.
    * Returns the current screen orientation.
    * Can be: landscape-primary, landscape-secondary,
    *         portrait-primary or portrait-secondary.
@@ -38,6 +39,7 @@ interface Screen : EventTarget {
   attribute EventHandler onmozorientationchange;
 
   /**
+   * DEPRECATED, use ScreenOrientation API instead.
    * Lock screen orientation to the specified type.
    */
   [Throws, UnsafeInPrerendering]
@@ -46,8 +48,14 @@ interface Screen : EventTarget {
   boolean mozLockOrientation(sequence<DOMString> orientation);
 
   /**
+   * DEPRECATED, use ScreenOrientation API instead.
    * Unlock the screen orientation.
    */
   [UnsafeInPrerendering]
   void mozUnlockOrientation();
 };
+
+// https://w3c.github.io/screen-orientation
+partial interface Screen {
+  readonly attribute ScreenOrientation orientation;
+};
diff --git a/dom/webidl/ScreenOrientation.webidl b/dom/webidl/ScreenOrientation.webidl
new file mode 100644
index 0000000000..48a2c11702
--- /dev/null
+++ b/dom/webidl/ScreenOrientation.webidl
@@ -0,0 +1,42 @@
+/* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * The origin of this IDL file is
+ * https://w3c.github.io/screen-orientation
+ *
+ * Copyright © 2014 W3C® (MIT, ERCIM, Keio, Beihang), All Rights
+ * Reserved. W3C liability, trademark and document use rules apply.
+ */
+
+enum OrientationType {
+  "portrait-primary",
+  "portrait-secondary",
+  "landscape-primary",
+  "landscape-secondary"
+};
+
+enum OrientationLockType {
+  "any",
+  "natural",
+  "landscape",
+  "portrait",
+  "portrait-primary",
+  "portrait-secondary",
+  "landscape-primary",
+  "landscape-secondary"
+};
+
+[UnsafeInPrerendering]
+interface ScreenOrientation : EventTarget {
+  [Throws]
+  Promise<void> lock(OrientationLockType orientation);
+  [Throws]
+  void unlock();
+  [Throws]
+  readonly attribute OrientationType type;
+  [Throws]
+  readonly attribute unsigned short angle;
+  attribute EventHandler onchange;
+};
diff --git a/dom/webidl/moz.build b/dom/webidl/moz.build
index 66e8168e92..25b0cdce98 100644
--- a/dom/webidl/moz.build
+++ b/dom/webidl/moz.build
@@ -385,6 +385,7 @@ WEBIDL_FILES = [
     'RGBColor.webidl',
     'RTCStatsReport.webidl',
     'Screen.webidl',
+    'ScreenOrientation.webidl',
     'ScriptProcessorNode.webidl',
     'ScrollAreaEvent.webidl',
     'ScrollBoxObject.webidl',
diff --git a/dom/workers/ServiceWorker.cpp b/dom/workers/ServiceWorker.cpp
index 4cf6fa61b4..46129c6c3d 100644
--- a/dom/workers/ServiceWorker.cpp
+++ b/dom/workers/ServiceWorker.cpp
@@ -52,11 +52,6 @@ ServiceWorker::ServiceWorker(nsPIDOMWindow* aWindow,
   MOZ_ASSERT(aInfo);
   MOZ_ASSERT(mSharedWorker);
 
-  if (aWindow) {
-    mDocument = aWindow->GetExtantDoc();
-    mWindow = aWindow->GetOuterWindow();
-  }
-
   // This will update our state too.
   mInfo->AppendWorker(this);
 }
@@ -74,7 +69,7 @@ NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION_INHERITED(ServiceWorker)
 NS_INTERFACE_MAP_END_INHERITING(DOMEventTargetHelper)
 
 NS_IMPL_CYCLE_COLLECTION_INHERITED(ServiceWorker, DOMEventTargetHelper,
-                                   mSharedWorker, mDocument, mWindow)
+                                   mSharedWorker)
 
 JSObject*
 ServiceWorker::WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto)
@@ -103,12 +98,9 @@ ServiceWorker::PostMessage(JSContext* aCx, JS::Handle<JS::Value> aMessage,
     return;
   }
 
-  MOZ_ASSERT(mDocument && mWindow,
-             "Cannot call PostMessage on a ServiceWorker object that doesn't "
-             "have a window");
-
-  nsAutoPtr<ServiceWorkerClientInfo> clientInfo(
-    new ServiceWorkerClientInfo(mDocument, mWindow));
+  nsCOMPtr<nsPIDOMWindow> window = do_QueryInterface(GetParentObject());
+  nsCOMPtr<nsIDocument> doc = window->GetExtantDoc();
+  nsAutoPtr<ServiceWorkerClientInfo> clientInfo(new ServiceWorkerClientInfo(doc));
 
   workerPrivate->PostMessageToServiceWorker(aCx, aMessage, aTransferable,
                                             clientInfo, aRv);
diff --git a/dom/workers/ServiceWorker.h b/dom/workers/ServiceWorker.h
index d744802714..9c438ba5c2 100644
--- a/dom/workers/ServiceWorker.h
+++ b/dom/workers/ServiceWorker.h
@@ -11,7 +11,6 @@
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/ServiceWorkerBinding.h" // For ServiceWorkerState.
 
-class nsIDocument;
 class nsPIDOMWindow;
 
 namespace mozilla {
@@ -92,10 +91,6 @@ private:
   // can be released and recreated as required rather than re-implement some of
   // the SharedWorker logic.
   nsRefPtr<SharedWorker> mSharedWorker;
-  // We need to keep the document and window alive for PostMessage to be able
-  // to access them.
-  nsCOMPtr<nsIDocument> mDocument;
-  nsCOMPtr<nsPIDOMWindow> mWindow;
 };
 
 } // namespace workers
diff --git a/dom/workers/ServiceWorkerClient.cpp b/dom/workers/ServiceWorkerClient.cpp
index 843f46fdf1..e52d26629e 100644
--- a/dom/workers/ServiceWorkerClient.cpp
+++ b/dom/workers/ServiceWorkerClient.cpp
@@ -29,8 +29,7 @@ NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(ServiceWorkerClient)
   NS_INTERFACE_MAP_ENTRY(nsISupports)
 NS_INTERFACE_MAP_END
 
-ServiceWorkerClientInfo::ServiceWorkerClientInfo(nsIDocument* aDoc,
-                                                 nsPIDOMWindow* aWindow)
+ServiceWorkerClientInfo::ServiceWorkerClientInfo(nsIDocument* aDoc)
   : mWindowId(0)
 {
   MOZ_ASSERT(aDoc);
@@ -55,7 +54,7 @@ ServiceWorkerClientInfo::ServiceWorkerClientInfo(nsIDocument* aDoc,
     NS_WARNING("Failed to get focus information.");
   }
 
-  nsRefPtr<nsGlobalWindow> outerWindow = static_cast<nsGlobalWindow*>(aWindow);
+  nsRefPtr<nsGlobalWindow> outerWindow = static_cast<nsGlobalWindow*>(aDoc->GetWindow());
   MOZ_ASSERT(outerWindow);
   if (!outerWindow->IsTopLevelWindow()) {
     mFrameType = FrameType::Nested;
@@ -135,7 +134,7 @@ private:
 
     JS::Rooted<JS::Value> messageData(aCx);
     if (!mBuffer.read(aCx, &messageData,
-                      WorkerStructuredCloneCallbacks(true), &closure)) {
+                      WorkerStructuredCloneCallbacks(), &closure)) {
       xpc::Throw(aCx, NS_ERROR_DOM_DATA_CLONE_ERR);
       return NS_ERROR_FAILURE;
     }
@@ -195,7 +194,7 @@ ServiceWorkerClient::PostMessage(JSContext* aCx, JS::Handle<JS::Value> aMessage,
     transferable.setObject(*array);
   }
 
-  const JSStructuredCloneCallbacks* callbacks = WorkerStructuredCloneCallbacks(false);
+  const JSStructuredCloneCallbacks* callbacks = WorkerStructuredCloneCallbacks();
 
   WorkerStructuredCloneClosure closure;
 
diff --git a/dom/workers/ServiceWorkerClient.h b/dom/workers/ServiceWorkerClient.h
index 375017fff9..fcaf2cc647 100644
--- a/dom/workers/ServiceWorkerClient.h
+++ b/dom/workers/ServiceWorkerClient.h
@@ -15,7 +15,6 @@
 #include "mozilla/dom/ClientBinding.h"
 
 class nsIDocument;
-class nsPIDOMWindow;
 
 namespace mozilla {
 namespace dom {
@@ -32,7 +31,7 @@ class ServiceWorkerClientInfo final
   friend class ServiceWorkerWindowClient;
 
 public:
-  ServiceWorkerClientInfo(nsIDocument* aDoc, nsPIDOMWindow* aWindow);
+  explicit ServiceWorkerClientInfo(nsIDocument* aDoc);
 
 private:
   nsString mClientId;
diff --git a/dom/workers/ServiceWorkerManager.cpp b/dom/workers/ServiceWorkerManager.cpp
index a724f45cef..8e83bf6cd9 100644
--- a/dom/workers/ServiceWorkerManager.cpp
+++ b/dom/workers/ServiceWorkerManager.cpp
@@ -3876,7 +3876,7 @@ ServiceWorkerManager::DispatchFetchEvent(const OriginAttributes& aOriginAttribut
     MOZ_ASSERT(aDoc);
     aRv = GetDocumentController(aDoc->GetInnerWindow(), failRunnable,
                                 getter_AddRefs(serviceWorker));
-    clientInfo = new ServiceWorkerClientInfo(aDoc, aDoc->GetWindow());
+    clientInfo = new ServiceWorkerClientInfo(aDoc);
   } else {
     nsCOMPtr<nsIChannel> internalChannel;
     aRv = aChannel->GetChannel(getter_AddRefs(internalChannel));
@@ -4261,7 +4261,7 @@ EnumControlledDocuments(nsISupports* aKey,
     return PL_DHASH_NEXT;
   }
 
-  ServiceWorkerClientInfo clientInfo(document, document->GetWindow());
+  ServiceWorkerClientInfo clientInfo(document);
   data->mDocuments.AppendElement(clientInfo);
 
   return PL_DHASH_NEXT;
diff --git a/dom/workers/ServiceWorkerWindowClient.cpp b/dom/workers/ServiceWorkerWindowClient.cpp
index 8e0f531bff..3e0e2a06d6 100644
--- a/dom/workers/ServiceWorkerWindowClient.cpp
+++ b/dom/workers/ServiceWorkerWindowClient.cpp
@@ -91,9 +91,14 @@ public:
     UniquePtr<ServiceWorkerClientInfo> clientInfo;
 
     if (window) {
-      nsContentUtils::DispatchChromeEvent(window->GetExtantDoc(), window->GetOuterWindow(), NS_LITERAL_STRING("DOMServiceWorkerFocusClient"), true, true);
-      clientInfo.reset(new ServiceWorkerClientInfo(window->GetDocument(),
-                                                   window->GetOuterWindow()));
+      nsCOMPtr<nsIDocument> doc = window->GetDocument();
+      if (doc) {
+        nsContentUtils::DispatchChromeEvent(doc,
+                                            window->GetOuterWindow(),
+                                            NS_LITERAL_STRING("DOMServiceWorkerFocusClient"),
+                                            true, true);
+        clientInfo.reset(new ServiceWorkerClientInfo(doc));
+      }
     }
 
     DispatchResult(Move(clientInfo));
diff --git a/dom/workers/WorkerPrivate.cpp b/dom/workers/WorkerPrivate.cpp
index 179da982e9..8e1cef4b5e 100644
--- a/dom/workers/WorkerPrivate.cpp
+++ b/dom/workers/WorkerPrivate.cpp
@@ -406,8 +406,7 @@ EnsureBlobForBackgroundManager(BlobImpl* aBlobImpl,
 
 already_AddRefed<Blob>
 ReadBlobOrFileNoWrap(JSContext* aCx,
-                     JSStructuredCloneReader* aReader,
-                     bool aIsMainThread)
+                     JSStructuredCloneReader* aReader)
 {
   MOZ_ASSERT(aCx);
   MOZ_ASSERT(aReader);
@@ -426,14 +425,11 @@ ReadBlobOrFileNoWrap(JSContext* aCx,
   MOZ_ASSERT(blobImpl);
 
   nsCOMPtr<nsISupports> parent;
-  if (aIsMainThread) {
-    AssertIsOnMainThread();
-
+  if (NS_IsMainThread()) {
     nsCOMPtr<nsIScriptGlobalObject> scriptGlobal =
       nsJSUtils::GetStaticScriptGlobal(JS::CurrentGlobalOrNull(aCx));
     parent = do_QueryInterface(scriptGlobal);
   } else {
-    MOZ_ASSERT(!NS_IsMainThread());
     WorkerPrivate* workerPrivate = GetWorkerPrivateFromContext(aCx);
     MOZ_ASSERT(workerPrivate);
 
@@ -450,10 +446,9 @@ ReadBlobOrFileNoWrap(JSContext* aCx,
 void
 ReadBlobOrFile(JSContext* aCx,
                JSStructuredCloneReader* aReader,
-               bool aIsMainThread,
                JS::MutableHandle<JSObject*> aBlobOrFile)
 {
-  nsRefPtr<Blob> blob = ReadBlobOrFileNoWrap(aCx, aReader, aIsMainThread);
+  nsRefPtr<Blob> blob = ReadBlobOrFileNoWrap(aCx, aReader);
   aBlobOrFile.set(blob->WrapObject(aCx, nullptr));
 }
 
@@ -461,7 +456,6 @@ ReadBlobOrFile(JSContext* aCx,
 void
 ReadFormData(JSContext* aCx,
              JSStructuredCloneReader* aReader,
-             bool aIsMainThread,
              uint32_t aCount,
              JS::MutableHandle<JSObject*> aFormData)
 {
@@ -470,8 +464,7 @@ ReadFormData(JSContext* aCx,
   MOZ_ASSERT(!aFormData);
 
   nsCOMPtr<nsISupports> parent;
-  if (aIsMainThread) {
-    AssertIsOnMainThread();
+  if (NS_IsMainThread()) {
     nsCOMPtr<nsIScriptGlobalObject> scriptGlobal =
       nsJSUtils::GetStaticScriptGlobal(JS::CurrentGlobalOrNull(aCx));
     parent = do_QueryInterface(scriptGlobal);
@@ -502,7 +495,7 @@ ReadFormData(JSContext* aCx,
     if (isFile) {
       // Read out the tag since the blob reader isn't expecting it.
       MOZ_ALWAYS_TRUE(JS_ReadUint32Pair(aReader, &dummy, &dummy));
-      nsRefPtr<Blob> blob = ReadBlobOrFileNoWrap(aCx, aReader, aIsMainThread);
+      nsRefPtr<Blob> blob = ReadBlobOrFileNoWrap(aCx, aReader);
       MOZ_ASSERT(blob);
       formData->Append(name, *blob, thirdArg);
     } else {
@@ -516,28 +509,29 @@ ReadFormData(JSContext* aCx,
 }
 
 bool
-WriteBlobOrFile(JSContext* aCx,
-                JSStructuredCloneWriter* aWriter,
-                BlobImpl* aBlobOrBlobImpl,
+WriteBlobOrFile(JSStructuredCloneWriter* aWriter,
+                BlobImpl* aBlobImpl,
                 WorkerStructuredCloneClosure& aClosure)
 {
-  MOZ_ASSERT(aCx);
   MOZ_ASSERT(aWriter);
-  MOZ_ASSERT(aBlobOrBlobImpl);
+  MOZ_ASSERT(aBlobImpl);
 
-  nsRefPtr<BlobImpl> blobImpl = EnsureBlobForBackgroundManager(aBlobOrBlobImpl);
-  MOZ_ASSERT(blobImpl);
-
-  aBlobOrBlobImpl = blobImpl;
-
-  if (NS_WARN_IF(!JS_WriteUint32Pair(aWriter, DOMWORKER_SCTAG_BLOB, 0)) ||
-      NS_WARN_IF(!JS_WriteBytes(aWriter,
-                                &aBlobOrBlobImpl,
-                                sizeof(aBlobOrBlobImpl)))) {
+  if (!aBlobImpl->MayBeClonedToOtherThreads()) {
+    NS_WARNING("Not all the blob implementations can be sent between threads.");
     return false;
   }
 
-  aClosure.mClonedObjects.AppendElement(aBlobOrBlobImpl);
+  nsRefPtr<BlobImpl> blobImpl = EnsureBlobForBackgroundManager(aBlobImpl);
+  MOZ_ASSERT(blobImpl);
+
+  aBlobImpl = blobImpl;
+
+  if (NS_WARN_IF(!JS_WriteUint32Pair(aWriter, DOMWORKER_SCTAG_BLOB, 0)) ||
+      NS_WARN_IF(!JS_WriteBytes(aWriter, &aBlobImpl, sizeof(aBlobImpl)))) {
+    return false;
+  }
+
+  aClosure.mClonedObjects.AppendElement(aBlobImpl);
   return true;
 }
 
@@ -565,7 +559,8 @@ WriteFormData(JSContext* aCx,
     return false;
   }
 
-  class MOZ_STACK_CLASS Closure {
+  class MOZ_STACK_CLASS Closure final
+  {
     JSContext* mCx;
     JSStructuredCloneWriter* mWriter;
     WorkerStructuredCloneClosure& mClones;
@@ -590,7 +585,8 @@ WriteFormData(JSContext* aCx,
       }
 
       if (isFile) {
-        if (!WriteBlobOrFile(closure->mCx, closure->mWriter, aFile->Impl(), closure->mClones)) {
+        if (!WriteBlobOrFile(closure->mWriter, aFile->Impl(),
+                             closure->mClones)) {
           return false;
         }
       } else {
@@ -613,27 +609,27 @@ struct WorkerStructuredCloneCallbacks
   Read(JSContext* aCx, JSStructuredCloneReader* aReader, uint32_t aTag,
        uint32_t aData, void* aClosure)
   {
-    JS::Rooted<JSObject*> result(aCx);
-
     // See if object is a nsIDOMBlob pointer.
     if (aTag == DOMWORKER_SCTAG_BLOB) {
       MOZ_ASSERT(!aData);
 
       JS::Rooted<JSObject*> blobOrFile(aCx);
-      ReadBlobOrFile(aCx, aReader, /* aIsMainThread */ false, &blobOrFile);
+      ReadBlobOrFile(aCx, aReader, &blobOrFile);
 
       return blobOrFile;
     }
+
     // See if the object is an ImageData.
-    else if (aTag == SCTAG_DOM_IMAGEDATA) {
+    if (aTag == SCTAG_DOM_IMAGEDATA) {
       MOZ_ASSERT(!aData);
       return ReadStructuredCloneImageData(aCx, aReader);
     }
+
     // See if the object is a FormData.
-    else if (aTag == DOMWORKER_SCTAG_FORMDATA) {
+    if (aTag == DOMWORKER_SCTAG_FORMDATA) {
       JS::Rooted<JSObject*> formData(aCx);
       // aData is the entry count.
-      ReadFormData(aCx, aReader, /* aIsMainThread */ false,  aData, &formData);
+      ReadFormData(aCx, aReader, aData, &formData);
       return formData;
     }
 
@@ -649,8 +645,7 @@ struct WorkerStructuredCloneCallbacks
                                               closure->mClonedImages, aData);
     }
 
-    Error(aCx, 0);
-    return nullptr;
+    return NS_DOMReadStructuredClone(aCx, aReader, aTag, aData, nullptr);
   }
 
   static bool
@@ -668,7 +663,7 @@ struct WorkerStructuredCloneCallbacks
         BlobImpl* blobImpl = blob->Impl();
         MOZ_ASSERT(blobImpl);
 
-        if (WriteBlobOrFile(aCx, aWriter, blobImpl, *closure)) {
+        if (WriteBlobOrFile(aWriter, blobImpl, *closure)) {
           return true;
         }
       }
@@ -702,8 +697,7 @@ struct WorkerStructuredCloneCallbacks
       }
     }
 
-    Error(aCx, 0);
-    return false;
+    return NS_DOMWriteStructuredClone(aCx, aWriter, aObj, nullptr);
   }
 
   static void
@@ -810,198 +804,6 @@ const JSStructuredCloneCallbacks gWorkerStructuredCloneCallbacks = {
   WorkerStructuredCloneCallbacks::FreeTransfer
 };
 
-struct MainThreadWorkerStructuredCloneCallbacks
-{
-  static JSObject*
-  Read(JSContext* aCx, JSStructuredCloneReader* aReader, uint32_t aTag,
-       uint32_t aData, void* aClosure)
-  {
-    AssertIsOnMainThread();
-
-    // See if object is a Blob/File pointer.
-    if (aTag == DOMWORKER_SCTAG_BLOB) {
-      MOZ_ASSERT(!aData);
-
-      JS::Rooted<JSObject*> blobOrFile(aCx);
-      ReadBlobOrFile(aCx, aReader, /* aIsMainThread */ true, &blobOrFile);
-
-      return blobOrFile;
-    }
-    // See if the object is a FormData.
-    else if (aTag == DOMWORKER_SCTAG_FORMDATA) {
-      JS::Rooted<JSObject*> formData(aCx);
-      // aData is the entry count.
-      ReadFormData(aCx, aReader, /* aIsMainThread */ true,  aData, &formData);
-      return formData;
-    }
-
-    // See if the object is a ImageBitmap
-    if (aTag == SCTAG_DOM_IMAGEBITMAP) {
-      NS_ASSERTION(aClosure, "Null pointer!");
-
-      // Get the current global object.
-      auto* closure = static_cast<WorkerStructuredCloneClosure*>(aClosure);
-      nsCOMPtr<nsIGlobalObject> parent = do_QueryInterface(closure->mParentWindow);
-      // aData is the index of the cloned image.
-      return ImageBitmap::ReadStructuredClone(aCx, aReader, parent,
-                                              closure->mClonedImages, aData);
-    }
-
-    JS_ClearPendingException(aCx);
-    return NS_DOMReadStructuredClone(aCx, aReader, aTag, aData, nullptr);
-  }
-
-  static bool
-  Write(JSContext* aCx, JSStructuredCloneWriter* aWriter,
-        JS::Handle<JSObject*> aObj, void* aClosure)
-  {
-    AssertIsOnMainThread();
-
-    NS_ASSERTION(aClosure, "Null pointer!");
-
-    auto* closure = static_cast<WorkerStructuredCloneClosure*>(aClosure);
-
-    // See if this is a Blob/File object.
-    {
-      nsRefPtr<Blob> blob;
-      if (NS_SUCCEEDED(UNWRAP_OBJECT(Blob, aObj, blob))) {
-        BlobImpl* blobImpl = blob->Impl();
-        MOZ_ASSERT(blobImpl);
-
-        if (!blobImpl->MayBeClonedToOtherThreads()) {
-          NS_WARNING("Not all the blob implementations can be sent between threads.");
-        } else if (WriteBlobOrFile(aCx, aWriter, blobImpl, *closure)) {
-          return true;
-        }
-      }
-    }
-
-    // Handle imageBitmap cloning
-    {
-      ImageBitmap* imageBitmap = nullptr;
-      if (NS_SUCCEEDED(UNWRAP_OBJECT(ImageBitmap, aObj, imageBitmap))) {
-        return ImageBitmap::WriteStructuredClone(aWriter,
-                                                 closure->mClonedImages,
-                                                 imageBitmap);
-      }
-    }
-
-    JS_ClearPendingException(aCx);
-    return NS_DOMWriteStructuredClone(aCx, aWriter, aObj, nullptr);
-  }
-
-  static void
-  Error(JSContext* aCx, uint32_t aErrorId)
-  {
-    AssertIsOnMainThread();
-
-    NS_DOMStructuredCloneError(aCx, aErrorId);
-  }
-};
-
-const JSStructuredCloneCallbacks gMainThreadWorkerStructuredCloneCallbacks = {
-  MainThreadWorkerStructuredCloneCallbacks::Read,
-  MainThreadWorkerStructuredCloneCallbacks::Write,
-  MainThreadWorkerStructuredCloneCallbacks::Error,
-  WorkerStructuredCloneCallbacks::ReadTransfer,
-  WorkerStructuredCloneCallbacks::Transfer,
-  WorkerStructuredCloneCallbacks::FreeTransfer
-};
-
-struct ChromeWorkerStructuredCloneCallbacks
-{
-  static JSObject*
-  Read(JSContext* aCx, JSStructuredCloneReader* aReader, uint32_t aTag,
-       uint32_t aData, void* aClosure)
-  {
-    return WorkerStructuredCloneCallbacks::Read(aCx, aReader, aTag, aData,
-                                                aClosure);
-  }
-
-  static bool
-  Write(JSContext* aCx, JSStructuredCloneWriter* aWriter,
-        JS::Handle<JSObject*> aObj, void* aClosure)
-  {
-    return WorkerStructuredCloneCallbacks::Write(aCx, aWriter, aObj, aClosure);
-  }
-
-  static void
-  Error(JSContext* aCx, uint32_t aErrorId)
-  {
-    return WorkerStructuredCloneCallbacks::Error(aCx, aErrorId);
-  }
-};
-
-const JSStructuredCloneCallbacks gChromeWorkerStructuredCloneCallbacks = {
-  ChromeWorkerStructuredCloneCallbacks::Read,
-  ChromeWorkerStructuredCloneCallbacks::Write,
-  ChromeWorkerStructuredCloneCallbacks::Error,
-  WorkerStructuredCloneCallbacks::ReadTransfer,
-  WorkerStructuredCloneCallbacks::Transfer,
-  WorkerStructuredCloneCallbacks::FreeTransfer
-};
-
-struct MainThreadChromeWorkerStructuredCloneCallbacks
-{
-  static JSObject*
-  Read(JSContext* aCx, JSStructuredCloneReader* aReader, uint32_t aTag,
-       uint32_t aData, void* aClosure)
-  {
-    AssertIsOnMainThread();
-
-    JSObject* clone =
-      MainThreadWorkerStructuredCloneCallbacks::Read(aCx, aReader, aTag, aData,
-                                                     aClosure);
-    if (clone) {
-      return clone;
-    }
-
-    clone =
-      ChromeWorkerStructuredCloneCallbacks::Read(aCx, aReader, aTag, aData,
-                                                 aClosure);
-    if (clone) {
-      return clone;
-    }
-
-    JS_ClearPendingException(aCx);
-    return NS_DOMReadStructuredClone(aCx, aReader, aTag, aData, nullptr);
-  }
-
-  static bool
-  Write(JSContext* aCx, JSStructuredCloneWriter* aWriter,
-        JS::Handle<JSObject*> aObj, void* aClosure)
-  {
-    AssertIsOnMainThread();
-
-    if (MainThreadWorkerStructuredCloneCallbacks::Write(aCx, aWriter, aObj,
-                                                        aClosure) ||
-        ChromeWorkerStructuredCloneCallbacks::Write(aCx, aWriter, aObj,
-                                                    aClosure) ||
-        NS_DOMWriteStructuredClone(aCx, aWriter, aObj, nullptr)) {
-      return true;
-    }
-
-    return false;
-  }
-
-  static void
-  Error(JSContext* aCx, uint32_t aErrorId)
-  {
-    AssertIsOnMainThread();
-
-    NS_DOMStructuredCloneError(aCx, aErrorId);
-  }
-};
-
-const JSStructuredCloneCallbacks gMainThreadChromeWorkerStructuredCloneCallbacks = {
-  MainThreadChromeWorkerStructuredCloneCallbacks::Read,
-  MainThreadChromeWorkerStructuredCloneCallbacks::Write,
-  MainThreadChromeWorkerStructuredCloneCallbacks::Error,
-  nullptr,
-  nullptr,
-  nullptr
-};
-
 class MainThreadReleaseRunnable final : public nsRunnable
 {
   nsTArray<nsCOMPtr<nsISupports>> mDoomed;
@@ -1346,7 +1148,7 @@ public:
 
     JS::Rooted<JS::Value> messageData(aCx);
     if (!mBuffer.read(aCx, &messageData,
-                      workers::WorkerStructuredCloneCallbacks(aIsMainThread),
+                      workers::WorkerStructuredCloneCallbacks(),
                       &closure)) {
       xpc::Throw(aCx, NS_ERROR_DOM_DATA_CLONE_ERR);
       return false;
@@ -1356,7 +1158,7 @@ public:
     nsresult rv =
       event->InitMessageEvent(NS_LITERAL_STRING("message"),
                               false /* non-bubbling */,
-                              true /* cancelable */,
+                              false /* non-cancelable */,
                               messageData,
                               EmptyString(),
                               EmptyString(),
@@ -3483,26 +3285,6 @@ WorkerPrivateParent<Derived>::PostMessageInternal(
     }
   }
 
-  const JSStructuredCloneCallbacks* callbacks;
-  if (GetParent()) {
-    if (IsChromeWorker()) {
-      callbacks = &gChromeWorkerStructuredCloneCallbacks;
-    }
-    else {
-      callbacks = &gWorkerStructuredCloneCallbacks;
-    }
-  }
-  else {
-    AssertIsOnMainThread();
-
-    if (IsChromeWorker()) {
-      callbacks = &gMainThreadChromeWorkerStructuredCloneCallbacks;
-    }
-    else {
-      callbacks = &gMainThreadWorkerStructuredCloneCallbacks;
-    }
-  }
-
   JS::Rooted<JS::Value> transferable(aCx, JS::UndefinedValue());
   if (aTransferable.WasPassed()) {
     const Sequence<JS::Value>& realTransferable = aTransferable.Value();
@@ -3527,7 +3309,8 @@ WorkerPrivateParent<Derived>::PostMessageInternal(
                              WorkerRunnable::WorkerThreadModifyBusyCount,
                              aToMessagePort, aMessagePortSerial);
 
-  if (!runnable->Write(aCx, aMessage, transferable, callbacks)) {
+  if (!runnable->Write(aCx, aMessage, transferable,
+                       &gWorkerStructuredCloneCallbacks)) {
     aRv.Throw(NS_ERROR_DOM_DATA_CLONE_ERR);
     return;
   }
@@ -3577,8 +3360,6 @@ WorkerPrivateParent<Derived>::DispatchMessageEventToMessagePort(
   AssertIsOnMainThread();
 
   JSAutoStructuredCloneBuffer buffer(Move(aBuffer));
-  const JSStructuredCloneCallbacks* callbacks =
-    WorkerStructuredCloneCallbacks(true);
 
   class MOZ_STACK_CLASS AutoCloneBufferCleaner final
   {
@@ -3608,7 +3389,9 @@ WorkerPrivateParent<Derived>::DispatchMessageEventToMessagePort(
   MOZ_ASSERT(aClosure.mMessagePorts.IsEmpty());
   closure.mMessagePortIdentifiers.SwapElements(aClosure.mMessagePortIdentifiers);
 
-  AutoCloneBufferCleaner bufferCleaner(buffer, callbacks, closure);
+  AutoCloneBufferCleaner bufferCleaner(buffer,
+                                       &gWorkerStructuredCloneCallbacks,
+                                       closure);
 
   SharedWorker* sharedWorker;
   if (!mSharedWorkers.Get(aMessagePortSerial, &sharedWorker)) {
@@ -3632,7 +3415,7 @@ WorkerPrivateParent<Derived>::DispatchMessageEventToMessagePort(
   JSContext* cx = jsapi.cx();
 
   JS::Rooted<JS::Value> data(cx);
-  if (!buffer.read(cx, &data, WorkerStructuredCloneCallbacks(true),
+  if (!buffer.read(cx, &data, &gWorkerStructuredCloneCallbacks,
                    &closure)) {
     return false;
   }
@@ -6292,17 +6075,13 @@ WorkerPrivate::PostMessageToParentInternal(
     transferable.setObject(*array);
   }
 
-  const JSStructuredCloneCallbacks* callbacks =
-    IsChromeWorker() ?
-    &gChromeWorkerStructuredCloneCallbacks :
-    &gWorkerStructuredCloneCallbacks;
-
   nsRefPtr<MessageEventRunnable> runnable =
     new MessageEventRunnable(this,
                              WorkerRunnable::ParentThreadUnchangedBusyCount,
                              aToMessagePort, aMessagePortSerial);
 
-  if (!runnable->Write(aCx, aMessage, transferable, callbacks)) {
+  if (!runnable->Write(aCx, aMessage, transferable,
+                       &gWorkerStructuredCloneCallbacks)) {
     aRv = NS_ERROR_DOM_DATA_CLONE_ERR;
     return;
   }
@@ -7445,19 +7224,9 @@ GetWorkerCrossThreadDispatcher(JSContext* aCx, JS::Value aWorker)
 }
 
 const JSStructuredCloneCallbacks*
-WorkerStructuredCloneCallbacks(bool aMainRuntime)
+WorkerStructuredCloneCallbacks()
 {
-  return aMainRuntime ?
-         &gMainThreadWorkerStructuredCloneCallbacks :
-         &gWorkerStructuredCloneCallbacks;
-}
-
-const JSStructuredCloneCallbacks*
-ChromeWorkerStructuredCloneCallbacks(bool aMainRuntime)
-{
-  return aMainRuntime ?
-         &gMainThreadChromeWorkerStructuredCloneCallbacks :
-         &gChromeWorkerStructuredCloneCallbacks;
+  return &gWorkerStructuredCloneCallbacks;
 }
 
 // Force instantiation.
diff --git a/dom/workers/WorkerPrivate.h b/dom/workers/WorkerPrivate.h
index 009b301841..0f95e58a12 100644
--- a/dom/workers/WorkerPrivate.h
+++ b/dom/workers/WorkerPrivate.h
@@ -1520,10 +1520,7 @@ enum WorkerStructuredDataType
 };
 
 const JSStructuredCloneCallbacks*
-WorkerStructuredCloneCallbacks(bool aMainRuntime);
-
-const JSStructuredCloneCallbacks*
-ChromeWorkerStructuredCloneCallbacks(bool aMainRuntime);
+WorkerStructuredCloneCallbacks();
 
 class AutoSyncLoopHolder
 {
diff --git a/dom/workers/XMLHttpRequest.cpp b/dom/workers/XMLHttpRequest.cpp
index 61df0d4da1..8ce46effff 100644
--- a/dom/workers/XMLHttpRequest.cpp
+++ b/dom/workers/XMLHttpRequest.cpp
@@ -1229,9 +1229,7 @@ EventRunnable::PreDispatch(JSContext* aCx, WorkerPrivate* aWorkerPrivate)
         if (doClone) {
           // Anything subject to GC must be cloned.
           const JSStructuredCloneCallbacks* callbacks =
-            aWorkerPrivate->IsChromeWorker() ?
-            workers::ChromeWorkerStructuredCloneCallbacks(true) :
-            workers::WorkerStructuredCloneCallbacks(true);
+            workers::WorkerStructuredCloneCallbacks();
 
           WorkerStructuredCloneClosure closure;
 
@@ -1344,9 +1342,7 @@ EventRunnable::WorkerRun(JSContext* aCx, WorkerPrivate* aWorkerPrivate)
         JSAutoStructuredCloneBuffer responseBuffer(Move(mResponseBuffer));
 
         const JSStructuredCloneCallbacks* callbacks =
-          aWorkerPrivate->IsChromeWorker() ?
-          workers::ChromeWorkerStructuredCloneCallbacks(false) :
-          workers::WorkerStructuredCloneCallbacks(false);
+          workers::WorkerStructuredCloneCallbacks();
 
         WorkerStructuredCloneClosure closure;
         closure.mClonedObjects.SwapElements(mResponseClosure.mClonedObjects);
@@ -1531,9 +1527,7 @@ SendRunnable::MainThreadRun()
     nsresult rv = NS_OK;
 
     const JSStructuredCloneCallbacks* callbacks =
-      mWorkerPrivate->IsChromeWorker() ?
-      workers::ChromeWorkerStructuredCloneCallbacks(true) :
-      workers::WorkerStructuredCloneCallbacks(true);
+      workers::WorkerStructuredCloneCallbacks();
 
     JS::Rooted<JS::Value> body(cx);
     if (mBody.read(cx, &body, callbacks, &mClosure)) {
@@ -2178,9 +2172,7 @@ XMLHttpRequest::Send(JS::Handle<JSObject*> aBody, ErrorResult& aRv)
   }
 
   const JSStructuredCloneCallbacks* callbacks =
-    mWorkerPrivate->IsChromeWorker() ?
-    ChromeWorkerStructuredCloneCallbacks(false) :
-    WorkerStructuredCloneCallbacks(false);
+    WorkerStructuredCloneCallbacks();
 
   WorkerStructuredCloneClosure closure;
 
@@ -2224,9 +2216,7 @@ XMLHttpRequest::Send(Blob& aBody, ErrorResult& aRv)
   }
 
   const JSStructuredCloneCallbacks* callbacks =
-    mWorkerPrivate->IsChromeWorker() ?
-    ChromeWorkerStructuredCloneCallbacks(false) :
-    WorkerStructuredCloneCallbacks(false);
+    WorkerStructuredCloneCallbacks();
 
   WorkerStructuredCloneClosure closure;
 
@@ -2262,9 +2252,7 @@ XMLHttpRequest::Send(nsFormData& aBody, ErrorResult& aRv)
   }
 
   const JSStructuredCloneCallbacks* callbacks =
-    mWorkerPrivate->IsChromeWorker() ?
-    ChromeWorkerStructuredCloneCallbacks(false) :
-    WorkerStructuredCloneCallbacks(false);
+    WorkerStructuredCloneCallbacks();
 
   JSAutoStructuredCloneBuffer buffer;
   WorkerStructuredCloneClosure closure;
diff --git a/js/xpconnect/wrappers/XrayWrapper.cpp b/js/xpconnect/wrappers/XrayWrapper.cpp
index ba6d6c56eb..9c7db6b80f 100644
--- a/js/xpconnect/wrappers/XrayWrapper.cpp
+++ b/js/xpconnect/wrappers/XrayWrapper.cpp
@@ -117,7 +117,7 @@ GetXrayType(JSObject* obj)
 }
 
 JSObject*
-XrayAwareCalleeGlobal(JSObject *fun)
+XrayAwareCalleeGlobal(JSObject* fun)
 {
   MOZ_ASSERT(js::IsFunctionObject(fun));
 
@@ -127,17 +127,17 @@ XrayAwareCalleeGlobal(JSObject *fun)
   }
 
   // The functions we expect here have the Xray wrapper they're associated with
-  // in their XRAY_DOM_FUNCTION_PARENT_WRAPPER_SLOT and, in a debug build, their
-  // JSNative in their XRAY_DOM_FUNCTION_NATIVE_SLOT_FOR_ASSERT.  Assert that
+  // in their XRAY_DOM_FUNCTION_PARENT_WRAPPER_SLOT and, in a debug build,
+  // themselves in their XRAY_DOM_FUNCTION_NATIVE_SLOT_FOR_SELF.  Assert that
   // last bit.
-  MOZ_ASSERT(js::GetFunctionNativeReserved(fun, XRAY_DOM_FUNCTION_NATIVE_SLOT_FOR_ASSERT).toPrivate() ==
-             js::GetFunctionObjectNative(fun));
+  MOZ_ASSERT(&js::GetFunctionNativeReserved(fun, XRAY_DOM_FUNCTION_NATIVE_SLOT_FOR_SELF).toObject() ==
+             fun);
 
   Value v =
       js::GetFunctionNativeReserved(fun, XRAY_DOM_FUNCTION_PARENT_WRAPPER_SLOT);
   MOZ_ASSERT(IsXrayWrapper(&v.toObject()));
 
-  JSObject *xrayTarget = js::UncheckedUnwrap(&v.toObject());
+  JSObject* xrayTarget = js::UncheckedUnwrap(&v.toObject());
   return js::GetGlobalForObjectCrossCompartment(xrayTarget);
 }
 
@@ -269,6 +269,21 @@ ReportWrapperDenial(JSContext* cx, HandleId id, WrapperDenialType type, const ch
     return true;
 }
 
+bool JSXrayTraits::getOwnPropertyFromWrapperIfSafe(JSContext* cx,
+                                                   HandleObject wrapper,
+                                                   HandleId id,
+                                                   MutableHandle<JSPropertyDescriptor> outDesc)
+{
+    MOZ_ASSERT(js::IsObjectInContextCompartment(wrapper, cx));
+    RootedObject target(cx, getTargetObject(wrapper));
+    {
+        JSAutoCompartment ac(cx, target);
+        if (!getOwnPropertyFromTargetIfSafe(cx, target, wrapper, id, outDesc))
+            return false;
+    }
+    return JS_WrapPropertyDescriptor(cx, outDesc);
+}
+
 bool JSXrayTraits::getOwnPropertyFromTargetIfSafe(JSContext* cx,
                                                   HandleObject target,
                                                   HandleObject wrapper,
@@ -382,12 +397,7 @@ JSXrayTraits::resolveOwnProperty(JSContext* cx, const Wrapper& jsWrapper,
         // "should" look like over Xrays, the underlying object is squishy enough
         // that it makes sense to just treat them like Objects for Xray purposes.
         if (key == JSProto_Object || key == JSProto_Array) {
-            {
-                JSAutoCompartment ac(cx, target);
-                if (!getOwnPropertyFromTargetIfSafe(cx, target, wrapper, id, desc))
-                    return false;
-            }
-            return JS_WrapPropertyDescriptor(cx, desc);
+            return getOwnPropertyFromWrapperIfSafe(cx, wrapper, id, desc);
         } else if (IsTypedArrayKey(key)) {
             if (IsArrayIndex(GetArrayIndexFromId(cx, id))) {
                 JS_ReportError(cx, "Accessing TypedArray data over Xrays is slow, and forbidden "
@@ -450,10 +460,8 @@ JSXrayTraits::resolveOwnProperty(JSContext* cx, const Wrapper& jsWrapper,
                 return true;
             }
         } else if (key == JSProto_RegExp) {
-            if (id == GetRTIdByIndex(cx, XPCJSRuntime::IDX_LASTINDEX)) {
-                JSAutoCompartment ac(cx, target);
-                return getOwnPropertyFromTargetIfSafe(cx, target, wrapper, id, desc);
-            }
+            if (id == GetRTIdByIndex(cx, XPCJSRuntime::IDX_LASTINDEX))
+                return getOwnPropertyFromWrapperIfSafe(cx, wrapper, id, desc);
         }
 
         // The rest of this function applies only to prototypes.
@@ -499,10 +507,8 @@ JSXrayTraits::resolveOwnProperty(JSContext* cx, const Wrapper& jsWrapper,
     }
 
     // Handle the 'lastIndex' property for RegExp prototypes.
-    if (key == JSProto_RegExp && id == GetRTIdByIndex(cx, XPCJSRuntime::IDX_LASTINDEX)) {
-        JSAutoCompartment ac(cx, target);
-        return getOwnPropertyFromTargetIfSafe(cx, target, wrapper, id, desc);
-    }
+    if (key == JSProto_RegExp && id == GetRTIdByIndex(cx, XPCJSRuntime::IDX_LASTINDEX))
+        return getOwnPropertyFromWrapperIfSafe(cx, wrapper, id, desc);
 
     // Grab the JSClass. We require all Xrayable classes to have a ClassSpec.
     const js::Class* clasp = js::GetObjectClass(target);
@@ -588,7 +594,7 @@ JSXrayTraits::resolveOwnProperty(JSContext* cx, const Wrapper& jsWrapper,
 }
 
 bool
-JSXrayTraits::delete_(JSContext *cx, HandleObject wrapper, HandleId id, ObjectOpResult &result)
+JSXrayTraits::delete_(JSContext* cx, HandleObject wrapper, HandleId id, ObjectOpResult& result)
 {
     RootedObject holder(cx, ensureHolder(cx, wrapper));
 
@@ -611,11 +617,11 @@ JSXrayTraits::delete_(JSContext *cx, HandleObject wrapper, HandleId id, ObjectOp
 }
 
 bool
-JSXrayTraits::defineProperty(JSContext *cx, HandleObject wrapper, HandleId id,
+JSXrayTraits::defineProperty(JSContext* cx, HandleObject wrapper, HandleId id,
                              Handle<JSPropertyDescriptor> desc,
                              Handle<JSPropertyDescriptor> existingDesc,
-                             ObjectOpResult &result,
-                             bool *defined)
+                             ObjectOpResult& result,
+                             bool* defined)
 {
     *defined = false;
     RootedObject holder(cx, ensureHolder(cx, wrapper));
@@ -1063,7 +1069,7 @@ XrayTraits::cloneExpandoChain(JSContext* cx, HandleObject dst, HandleObject src)
     // preserved when expandos were originally added to |src|. Assert the
     // wrapper for |src| has been preserved if it has expandos set.
     if (oldHead) {
-        nsISupports *identity = mozilla::dom::UnwrapDOMObjectToISupports(src);
+        nsISupports* identity = mozilla::dom::UnwrapDOMObjectToISupports(src);
         if (identity) {
             nsWrapperCache* cache = nullptr;
             CallQueryInterface(identity, &cache);
@@ -1244,7 +1250,7 @@ XPCWrappedNativeXrayTraits::resolveNativeProperty(JSContext* cx, HandleObject wr
         if (id != nsXPConnect::GetRuntimeInstance()->GetStringID(XPCJSRuntime::IDX_TO_STRING))
             return true;
 
-        JSFunction *toString = JS_NewFunction(cx, XrayToString, 0, 0, "toString");
+        JSFunction* toString = JS_NewFunction(cx, XrayToString, 0, 0, "toString");
         if (!toString)
             return false;
 
@@ -1442,10 +1448,10 @@ XPCWrappedNativeXrayTraits::resolveOwnProperty(JSContext* cx, const Wrapper& jsW
 }
 
 bool
-XPCWrappedNativeXrayTraits::defineProperty(JSContext *cx, HandleObject wrapper, HandleId id,
+XPCWrappedNativeXrayTraits::defineProperty(JSContext* cx, HandleObject wrapper, HandleId id,
                                            Handle<JSPropertyDescriptor> desc,
                                            Handle<JSPropertyDescriptor> existingDesc,
-                                           JS::ObjectOpResult &result, bool *defined)
+                                           JS::ObjectOpResult& result, bool* defined)
 {
     *defined = false;
     RootedObject holder(cx, singleton.ensureHolder(cx, wrapper));
@@ -1602,10 +1608,10 @@ DOMXrayTraits::resolveOwnProperty(JSContext* cx, const Wrapper& jsWrapper, Handl
 }
 
 bool
-DOMXrayTraits::defineProperty(JSContext *cx, HandleObject wrapper, HandleId id,
+DOMXrayTraits::defineProperty(JSContext* cx, HandleObject wrapper, HandleId id,
                               Handle<JSPropertyDescriptor> desc,
                               Handle<JSPropertyDescriptor> existingDesc,
-                              JS::ObjectOpResult &result, bool *defined)
+                              JS::ObjectOpResult& result, bool* defined)
 {
     // Check for an indexed property on a Window.  If that's happening, do
     // nothing but claim we defined it so it won't get added as an expando.
@@ -1685,7 +1691,7 @@ DOMXrayTraits::construct(JSContext* cx, HandleObject wrapper,
 }
 
 bool
-DOMXrayTraits::getPrototype(JSContext *cx, JS::HandleObject wrapper,
+DOMXrayTraits::getPrototype(JSContext* cx, JS::HandleObject wrapper,
                             JS::HandleObject target,
                             JS::MutableHandleObject protop)
 {
@@ -1816,8 +1822,8 @@ XrayToString(JSContext* cx, unsigned argc, Value* vp)
 
 template <typename Base, typename Traits>
 bool
-XrayWrapper<Base, Traits>::preventExtensions(JSContext *cx, HandleObject wrapper,
-                                             ObjectOpResult &result) const
+XrayWrapper<Base, Traits>::preventExtensions(JSContext* cx, HandleObject wrapper,
+                                             ObjectOpResult& result) const
 {
     // Xray wrappers are supposed to provide a clean view of the target
     // reflector, hiding any modifications by script in the target scope.  So
@@ -1957,7 +1963,7 @@ XrayWrapper<Base, Traits>::getOwnPropertyDescriptor(JSContext* cx, HandleObject
 // to the content object. This is ok, because the the expando object is only
 // ever accessed by code across the compartment boundary.
 static bool
-RecreateLostWaivers(JSContext *cx, const JSPropertyDescriptor *orig,
+RecreateLostWaivers(JSContext* cx, const JSPropertyDescriptor* orig,
                     MutableHandle<JSPropertyDescriptor> wrapped)
 {
     // Compute whether the original objects were waived, and implicitly, whether
@@ -2001,9 +2007,9 @@ RecreateLostWaivers(JSContext *cx, const JSPropertyDescriptor *orig,
 
 template <typename Base, typename Traits>
 bool
-XrayWrapper<Base, Traits>::defineProperty(JSContext *cx, HandleObject wrapper,
+XrayWrapper<Base, Traits>::defineProperty(JSContext* cx, HandleObject wrapper,
                                           HandleId id, Handle<JSPropertyDescriptor> desc,
-                                          ObjectOpResult &result) const
+                                          ObjectOpResult& result) const
 {
     assertEnteredPolicy(cx, wrapper, id, BaseProxyHandler::SET);
 
@@ -2075,7 +2081,7 @@ XrayWrapper<Base, Traits>::ownPropertyKeys(JSContext* cx, HandleObject wrapper,
 template <typename Base, typename Traits>
 bool
 XrayWrapper<Base, Traits>::delete_(JSContext* cx, HandleObject wrapper,
-                                   HandleId id, ObjectOpResult &result) const
+                                   HandleId id, ObjectOpResult& result) const
 {
     assertEnteredPolicy(cx, wrapper, id, BaseProxyHandler::SET);
 
@@ -2200,7 +2206,7 @@ XrayWrapper<Base, Traits>::defaultValue(JSContext* cx, HandleObject wrapper,
 
 template <typename Base, typename Traits>
 bool
-XrayWrapper<Base, Traits>::getPrototype(JSContext *cx, JS::HandleObject wrapper,
+XrayWrapper<Base, Traits>::getPrototype(JSContext* cx, JS::HandleObject wrapper,
                                         JS::MutableHandleObject protop) const
 {
     // We really only want this override for non-SecurityWrapper-inheriting
@@ -2233,8 +2239,8 @@ XrayWrapper<Base, Traits>::getPrototype(JSContext *cx, JS::HandleObject wrapper,
 
 template <typename Base, typename Traits>
 bool
-XrayWrapper<Base, Traits>::setPrototype(JSContext *cx, JS::HandleObject wrapper,
-                                        JS::HandleObject proto, JS::ObjectOpResult &result) const
+XrayWrapper<Base, Traits>::setPrototype(JSContext* cx, JS::HandleObject wrapper,
+                                        JS::HandleObject proto, JS::ObjectOpResult& result) const
 {
     // Do this only for non-SecurityWrapper-inheriting |Base|. See the comment
     // in getPrototype().
diff --git a/js/xpconnect/wrappers/XrayWrapper.h b/js/xpconnect/wrappers/XrayWrapper.h
index 8e6067a195..a66bebe4ce 100644
--- a/js/xpconnect/wrappers/XrayWrapper.h
+++ b/js/xpconnect/wrappers/XrayWrapper.h
@@ -18,9 +18,9 @@
 // the Xray wrapper they're associated with.
 #define XRAY_DOM_FUNCTION_PARENT_WRAPPER_SLOT 0
 // Slot where in debug builds Xray functions for Web IDL methods store
-// a pointer to their JSNative, just so we can assert that they're the
+// a pointer to their themselves, just so we can assert that they're the
 // sort of functions we expect.
-#define XRAY_DOM_FUNCTION_NATIVE_SLOT_FOR_ASSERT 1
+#define XRAY_DOM_FUNCTION_NATIVE_SLOT_FOR_SELF 1
 
 // Xray wrappers re-resolve the original native properties on the native
 // object and always directly access to those properties.
@@ -78,8 +78,8 @@ public:
                                     JS::HandleObject wrapper, JS::HandleObject holder,
                                     JS::HandleId id, JS::MutableHandle<JSPropertyDescriptor> desc);
 
-    bool delete_(JSContext *cx, JS::HandleObject wrapper, JS::HandleId id,
-                 JS::ObjectOpResult &result) {
+    bool delete_(JSContext* cx, JS::HandleObject wrapper, JS::HandleId id,
+                 JS::ObjectOpResult& result) {
         return result.succeed();
     }
 
@@ -132,10 +132,10 @@ public:
     virtual bool resolveOwnProperty(JSContext* cx, const js::Wrapper& jsWrapper, JS::HandleObject wrapper,
                                     JS::HandleObject holder, JS::HandleId id,
                                     JS::MutableHandle<JSPropertyDescriptor> desc) override;
-    bool defineProperty(JSContext *cx, JS::HandleObject wrapper, JS::HandleId id,
+    bool defineProperty(JSContext* cx, JS::HandleObject wrapper, JS::HandleId id,
                         JS::Handle<JSPropertyDescriptor> desc,
                         JS::Handle<JSPropertyDescriptor> existingDesc,
-                        JS::ObjectOpResult &result, bool *defined);
+                        JS::ObjectOpResult& result, bool* defined);
     virtual bool enumerateNames(JSContext* cx, JS::HandleObject wrapper, unsigned flags,
                                 JS::AutoIdVector& props);
     static bool call(JSContext* cx, JS::HandleObject wrapper,
@@ -184,22 +184,22 @@ public:
     virtual bool resolveOwnProperty(JSContext* cx, const js::Wrapper& jsWrapper, JS::HandleObject wrapper,
                                     JS::HandleObject holder, JS::HandleId id,
                                     JS::MutableHandle<JSPropertyDescriptor> desc) override;
-    bool defineProperty(JSContext *cx, JS::HandleObject wrapper, JS::HandleId id,
+    bool defineProperty(JSContext* cx, JS::HandleObject wrapper, JS::HandleId id,
                         JS::Handle<JSPropertyDescriptor> desc,
                         JS::Handle<JSPropertyDescriptor> existingDesc,
-                        JS::ObjectOpResult &result, bool *defined);
+                        JS::ObjectOpResult& result, bool* defined);
     virtual bool enumerateNames(JSContext* cx, JS::HandleObject wrapper, unsigned flags,
                                 JS::AutoIdVector& props);
     static bool call(JSContext* cx, JS::HandleObject wrapper,
                      const JS::CallArgs& args, const js::Wrapper& baseInstance);
-    static bool construct(JSContext *cx, JS::HandleObject wrapper,
-                          const JS::CallArgs &args, const js::Wrapper& baseInstance);
+    static bool construct(JSContext* cx, JS::HandleObject wrapper,
+                          const JS::CallArgs& args, const js::Wrapper& baseInstance);
 
-    static bool getPrototype(JSContext *cx, JS::HandleObject wrapper,
+    static bool getPrototype(JSContext* cx, JS::HandleObject wrapper,
                              JS::HandleObject target,
                              JS::MutableHandleObject protop);
 
-    virtual void preserveWrapper(JSObject *target) override;
+    virtual void preserveWrapper(JSObject* target) override;
 
     virtual JSObject* createHolder(JSContext* cx, JSObject* wrapper) override;
 
@@ -225,12 +225,12 @@ public:
                                     JS::HandleObject holder, JS::HandleId id,
                                     JS::MutableHandle<JSPropertyDescriptor> desc) override;
 
-    bool delete_(JSContext *cx, JS::HandleObject wrapper, JS::HandleId id, JS::ObjectOpResult &result);
+    bool delete_(JSContext* cx, JS::HandleObject wrapper, JS::HandleId id, JS::ObjectOpResult& result);
 
-    bool defineProperty(JSContext *cx, JS::HandleObject wrapper, JS::HandleId id,
+    bool defineProperty(JSContext* cx, JS::HandleObject wrapper, JS::HandleId id,
                         JS::Handle<JSPropertyDescriptor> desc,
                         JS::Handle<JSPropertyDescriptor> existingDesc,
-                        JS::ObjectOpResult &result, bool *defined);
+                        JS::ObjectOpResult& result, bool* defined);
 
     virtual bool enumerateNames(JSContext* cx, JS::HandleObject wrapper, unsigned flags,
                                 JS::AutoIdVector& props);
@@ -322,6 +322,13 @@ public:
         return static_cast<JSProtoKey>(key);
     }
 
+    // Operates in the wrapper compartment.
+    static bool getOwnPropertyFromWrapperIfSafe(JSContext* cx,
+                                                JS::HandleObject wrapper,
+                                                JS::HandleId id,
+                                                JS::MutableHandle<JSPropertyDescriptor> desc);
+
+    // Like the above, but operates in the target compartment.
     static bool getOwnPropertyFromTargetIfSafe(JSContext* cx,
                                                JS::HandleObject target,
                                                JS::HandleObject wrapper,
@@ -350,14 +357,14 @@ public:
         MOZ_CRASH("resolveNativeProperty hook should never be called with HasPrototype = 1");
     }
 
-    virtual bool resolveOwnProperty(JSContext *cx, const js::Wrapper &jsWrapper, JS::HandleObject wrapper,
+    virtual bool resolveOwnProperty(JSContext* cx, const js::Wrapper& jsWrapper, JS::HandleObject wrapper,
                                     JS::HandleObject holder, JS::HandleId id,
                                     JS::MutableHandle<JSPropertyDescriptor> desc) override;
 
-    bool defineProperty(JSContext *cx, JS::HandleObject wrapper, JS::HandleId id,
+    bool defineProperty(JSContext* cx, JS::HandleObject wrapper, JS::HandleId id,
                         JS::Handle<JSPropertyDescriptor> desc,
                         JS::Handle<JSPropertyDescriptor> existingDesc,
-                        JS::ObjectOpResult &result, bool *defined)
+                        JS::ObjectOpResult& result, bool* defined)
     {
         *defined = false;
         return true;
@@ -385,7 +392,7 @@ public:
         return false;
     }
 
-    bool getPrototype(JSContext *cx, JS::HandleObject wrapper,
+    bool getPrototype(JSContext* cx, JS::HandleObject wrapper,
                       JS::HandleObject target,
                       JS::MutableHandleObject protop)
     {
@@ -434,7 +441,7 @@ class XrayWrapper : public Base {
     virtual bool ownPropertyKeys(JSContext* cx, JS::Handle<JSObject*> wrapper,
                                  JS::AutoIdVector& props) const override;
     virtual bool delete_(JSContext* cx, JS::Handle<JSObject*> wrapper,
-                         JS::Handle<jsid> id, JS::ObjectOpResult &result) const override;
+                         JS::Handle<jsid> id, JS::ObjectOpResult& result) const override;
     virtual bool enumerate(JSContext* cx, JS::Handle<JSObject*> wrapper,
                            JS::MutableHandle<JSObject*> objp) const override;
     virtual bool getPrototype(JSContext* cx, JS::HandleObject wrapper,
@@ -442,9 +449,9 @@ class XrayWrapper : public Base {
     virtual bool setPrototype(JSContext* cx, JS::HandleObject wrapper,
                               JS::HandleObject proto, JS::ObjectOpResult& result) const override;
     virtual bool setImmutablePrototype(JSContext* cx, JS::HandleObject wrapper,
-                                       bool *succeeded) const override;
-    virtual bool preventExtensions(JSContext *cx, JS::Handle<JSObject*> wrapper,
-                                   JS::ObjectOpResult &result) const override;
+                                       bool* succeeded) const override;
+    virtual bool preventExtensions(JSContext* cx, JS::Handle<JSObject*> wrapper,
+                                   JS::ObjectOpResult& result) const override;
     virtual bool isExtensible(JSContext* cx, JS::Handle<JSObject*> wrapper, bool* extensible) const override;
     virtual bool has(JSContext* cx, JS::Handle<JSObject*> wrapper, JS::Handle<jsid> id,
                      bool* bp) const override;
@@ -526,7 +533,7 @@ public:
                      JS::Handle<jsid> id, JS::MutableHandle<JS::Value> vp) const override;
     virtual bool set(JSContext* cx, JS::Handle<JSObject*> proxy, JS::Handle<jsid> id,
                      JS::Handle<JS::Value> v, JS::Handle<JS::Value> receiver,
-                     JS::ObjectOpResult &result) const override;
+                     JS::ObjectOpResult& result) const override;
 
     virtual bool getPropertyDescriptor(JSContext* cx, JS::Handle<JSObject*> proxy,
                                        JS::Handle<jsid> id,
diff --git a/testing/web-platform/meta/screen-orientation/lock-bad-argument.html.ini b/testing/web-platform/meta/screen-orientation/lock-bad-argument.html.ini
index c51e31520e..624ba7b227 100644
--- a/testing/web-platform/meta/screen-orientation/lock-bad-argument.html.ini
+++ b/testing/web-platform/meta/screen-orientation/lock-bad-argument.html.ini
@@ -1,6 +1,5 @@
 [lock-bad-argument.html]
   type: testharness
-  expected: ERROR
   [Test that screen.orientation.lock() throws when the input isn't valid.]
-    expected: NOTRUN
+    expected: FAIL
 
diff --git a/testing/web-platform/meta/screen-orientation/lock-basic.html.ini b/testing/web-platform/meta/screen-orientation/lock-basic.html.ini
index d7ce5dfc89..2867b2bd3e 100644
--- a/testing/web-platform/meta/screen-orientation/lock-basic.html.ini
+++ b/testing/web-platform/meta/screen-orientation/lock-basic.html.ini
@@ -1,8 +1,6 @@
 [lock-basic.html]
   type: testharness
-  [Test that screen.orientation.unlock() doesn't throw when there is no lock]
-    expected: FAIL
-
+  expected: TIMEOUT
   [Test that screen.orientation.lock returns a pending promise.]
-    expected: FAIL
+    expected: TIMEOUT
 
diff --git a/testing/web-platform/meta/screen-orientation/lock-sandboxed-iframe.html.ini b/testing/web-platform/meta/screen-orientation/lock-sandboxed-iframe.html.ini
index d9787fc7aa..8948f8a2f2 100644
--- a/testing/web-platform/meta/screen-orientation/lock-sandboxed-iframe.html.ini
+++ b/testing/web-platform/meta/screen-orientation/lock-sandboxed-iframe.html.ini
@@ -2,7 +2,7 @@
   type: testharness
   expected: TIMEOUT
   [Test without 'allow-orientation-lock' sandboxing directive]
-    expected: NOTRUN
+    expected: FAIL
 
   [Test with 'allow-orientation-lock' sandboxing directive]
     expected: NOTRUN
diff --git a/testing/web-platform/meta/screen-orientation/onchange-event-subframe.html.ini b/testing/web-platform/meta/screen-orientation/onchange-event-subframe.html.ini
index 9101e9ef97..614ed43b87 100644
--- a/testing/web-platform/meta/screen-orientation/onchange-event-subframe.html.ini
+++ b/testing/web-platform/meta/screen-orientation/onchange-event-subframe.html.ini
@@ -1,6 +1,6 @@
 [onchange-event-subframe.html]
   type: testharness
-  expected: ERROR
+  expected: TIMEOUT
   [Test subframes receive orientation change events]
     expected: NOTRUN
 
diff --git a/testing/web-platform/meta/screen-orientation/onchange-event.html.ini b/testing/web-platform/meta/screen-orientation/onchange-event.html.ini
index af9d28ebbf..36bac914fb 100644
--- a/testing/web-platform/meta/screen-orientation/onchange-event.html.ini
+++ b/testing/web-platform/meta/screen-orientation/onchange-event.html.ini
@@ -1,6 +1,6 @@
 [onchange-event.html]
   type: testharness
-  expected: ERROR
+  expected: TIMEOUT
   [Test that orientationchange event is fired when the orientation changes.]
     expected: NOTRUN
 
diff --git a/testing/web-platform/meta/screen-orientation/orientation-api.html.ini b/testing/web-platform/meta/screen-orientation/orientation-api.html.ini
deleted file mode 100644
index f1c792933d..0000000000
--- a/testing/web-platform/meta/screen-orientation/orientation-api.html.ini
+++ /dev/null
@@ -1,11 +0,0 @@
-[orientation-api.html]
-  type: testharness
-  [Test that the Screen Orientation API is present.]
-    expected: FAIL
-
-  [Test Screen Orientation API property types.]
-    expected: FAIL
-
-  [Test that screen.orientation is an EventTarget.]
-    expected: FAIL
-
diff --git a/testing/web-platform/meta/screen-orientation/orientation-reading.html.ini b/testing/web-platform/meta/screen-orientation/orientation-reading.html.ini
index 3ad9413040..b31f157803 100644
--- a/testing/web-platform/meta/screen-orientation/orientation-reading.html.ini
+++ b/testing/web-platform/meta/screen-orientation/orientation-reading.html.ini
@@ -1,14 +1,8 @@
 [orientation-reading.html]
   type: testharness
-  [Test screen.orientation properties]
-    expected: FAIL
-
   [Test screen.orientation default values.]
     expected: FAIL
 
-  [Test that screen.orientation properties are not writable]
-    expected: FAIL
-
   [Test that screen.orientation values change if the orientation changes]
     expected: FAIL
 
diff --git a/testing/web-platform/meta/workers/interfaces/DedicatedWorkerGlobalScope/postMessage/message-event.html.ini b/testing/web-platform/meta/workers/interfaces/DedicatedWorkerGlobalScope/postMessage/message-event.html.ini
deleted file mode 100644
index c810dcf32e..0000000000
--- a/testing/web-platform/meta/workers/interfaces/DedicatedWorkerGlobalScope/postMessage/message-event.html.ini
+++ /dev/null
@@ -1,5 +0,0 @@
-[message-event.html]
-  type: testharness
-  [Properties of the 'message' event]
-    expected: FAIL
-