import changes from `dev' branch of rmottola/Arctic-Fox:

- Bug 1256731 - patch 2 - Notify front-end code when screen resolution changes on Windows, so that TabsInTitlebar code can refresh its computations. r=gijs,emk (4b0baacc83)
- Bug 1219215 - part 1: remove window-drag bindings and other callers of WindowDraggingUtils, replace with using window-dragging region everywhere, r=dao,felipe (4c8f9ebcd4)
- Bug 1253498 - Update pdf.js to version 1.4.121. r=bdahl (562abb5b6a)
- Bug 1256037 - Update pdf.js to version 1.4.137. r=bdahl (adc91322e2)
- Bug 1261352 - Update pdf.js to version 1.4.185. r=bdahl, r=Mossop (04584d13db)
- Bug 1263067 - Update pdf.js to version 1.4.213. r=bdahl, r=sicking (7e484dfad1)
- Bug 1256165 - fit to width again after the restore session button is added, r=Felipe (4a9ccc6c04)
- Bug 1261307: Convert |StreamSocketConsumer::ReceiveSocketData| to |UniquePtr|, r=nfroyd (65088da288)
- Bug 1264377. Get rid of some unnecessary custom JSClass hook functions in xpconnect sandboxes and DOM simple globals. r=bholley (578df7a830)
- Bug 1249518 - Make DaemonSocketPDU able to send multiple file descriptors in single unit. r=tzimmermann (1bf04f8f43)

browser/base/content/abouthome/aboutHome.js

@@ -27,6 +27,10 @@ var searchText;
 var gInitialized = false;
 var gObserver = new MutationObserver(function (mutations) {
   for (let mutation of mutations) {
+    // The addition of the restore session button changes our width:
+    if (mutation.attributeName == "session") {
+      fitToWidth();
+    }
     if (mutation.attributeName == "snippetsVersion") {
       if (!gInitialized) {
         ensureSnippetsMapThen(loadSnippets);
@@ -41,6 +45,7 @@ window.addEventListener("pageshow", function () {
   // Delay search engine setup, cause browser.js::BrowserOnAboutPageLoad runs
   // later and may use asynchronous getters.
   window.gObserver.observe(document.documentElement, { attributes: true });
+  window.gObserver.observe(document.getElementById("launcher"), { attributes: true });
   fitToWidth();
   setupSearch();
   window.addEventListener("resize", fitToWidth);

browser/base/content/browser-tabsintitlebar.js

@@ -190,21 +190,6 @@ var TabsInTitlebar = {
                                                                : titlebarContentHeight;
       titlebar.style.marginBottom = "-" + baseHeight + "px";
 
-      if (!this._draghandles) {
-        this._draghandles = {};
-        let tmp = {};
-        Components.utils.import("resource://gre/modules/WindowDraggingUtils.jsm", tmp);
-
-        let mouseDownCheck = function () {
-          return !this._dragBindingAlive && TabsInTitlebar.enabled;
-        };
-
-        this._draghandles.tabsToolbar = new tmp.WindowDraggingElement(tabsToolbar);
-        this._draghandles.tabsToolbar.mouseDownCheck = mouseDownCheck;
-
-        this._draghandles.navToolbox = new tmp.WindowDraggingElement(gNavToolbox);
-        this._draghandles.navToolbox.mouseDownCheck = mouseDownCheck;
-      }
     } else {
       document.documentElement.removeAttribute("tabsintitlebar");
     }

browser/base/content/browser.css

@@ -18,6 +18,12 @@ browser[remote="true"] {
   -moz-binding: url("chrome://browser/content/tabbrowser.xml#tabbrowser-remote-browser");
 }
 
+%ifdef XP_MACOSX
+#toolbar-menubar {
+  -moz-binding: url("chrome://browser/content/customizableui/toolbar.xml#toolbar-menubar-stub");
+}
+%endif
+
 browser[frameType="social"][remote="true"] {
   -moz-binding: url("chrome://global/content/bindings/remote-browser.xml#remote-browser");
 }
@@ -124,6 +130,7 @@ toolbar[printpreview="true"] {
 
 #titlebar {
   -moz-binding: url("chrome://global/content/bindings/general.xml#windowdragbox");
+  -moz-window-dragging: drag;
 }
 
 #titlebar-spacer {
@@ -136,6 +143,29 @@ toolbar[printpreview="true"] {
 }
 %endif
 
+%if !defined(MOZ_WIDGET_GTK) && !defined(MOZ_WIDGET_QT)
+#TabsToolbar > .private-browsing-indicator {
+  -moz-box-ordinal-group: 1000;
+}
+%endif
+
+%ifdef XP_WIN
+#main-window[sizemode="maximized"] #titlebar-buttonbox {
+  -moz-appearance: -moz-window-button-box-maximized;
+}
+
+#main-window[tabletmode] #titlebar-min,
+#main-window[tabletmode] #titlebar-max {
+  display: none !important;
+}
+
+#main-window[tabsintitlebar] #TabsToolbar,
+#main-window[tabsintitlebar] #toolbar-menubar:not([autohide=true]),
+#main-window[tabsintitlebar] #navigator-toolbox > toolbar:not(#toolbar-menubar):-moz-lwtheme {
+  -moz-window-dragging: drag;
+}
+%endif
+
 #main-window[inDOMFullscreen] #sidebar-box,
 #main-window[inDOMFullscreen] #sidebar-splitter {
   visibility: collapse;
@@ -184,6 +214,17 @@ toolbar[mode="icons"] > #reload-button[displaystop] {
 }
 %endif
 
+
+/* Ensure that empty parts of the bookmarks container can be dragged on OSX, and on other OSes
+ * only when a lwtheme is in use. */
+%ifdef XP_MACOSX
+#PlacesToolbarItems {
+%else
+#main-window[tabsintitlebar] #PlacesToolbarItems:-moz-lwtheme {
+%endif
+  -moz-window-dragging: drag;
+}
+
 #navigator-toolbox[fullscreenShouldAnimate] {
   transition: 1.5s margin-top ease-out;
 }

browser/extensions/pdfjs/README.mozilla

@@ -1,3 +1,3 @@
 This is the pdf.js project output, https://github.com/mozilla/pdf.js
 
-Current extension version is: 1.4.95
+Current extension version is: 1.4.213

browser/extensions/pdfjs/content/PdfStreamConverter.jsm

@@ -264,11 +264,9 @@ ChromeActions.prototype = {
     var extHelperAppSvc =
           Cc['@mozilla.org/uriloader/external-helper-app-service;1'].
              getService(Ci.nsIExternalHelperAppService);
-    var frontWindow = Cc['@mozilla.org/embedcomp/window-watcher;1'].
-                         getService(Ci.nsIWindowWatcher).activeWindow;
 
     var docIsPrivate = this.isInPrivateBrowsing();
-    var netChannel = createNewChannel(blobUri, frontWindow.document, null);
+    var netChannel = createNewChannel(blobUri, this.domWindow.document, null);
     if ('nsIPrivateBrowsingChannel' in Ci &&
         netChannel instanceof Ci.nsIPrivateBrowsingChannel) {
       netChannel.setPrivate(docIsPrivate);
@@ -304,10 +302,14 @@ ChromeActions.prototype = {
       var listener = {
         extListener: null,
         onStartRequest: function(aRequest, aContext) {
+          var loadContext = self.domWindow
+                                .QueryInterface(Ci.nsIInterfaceRequestor)
+                                .getInterface(Ci.nsIWebNavigation)
+                                .QueryInterface(Ci.nsILoadContext);
           this.extListener = extHelperAppSvc.doContent(
             (data.isAttachment ? 'application/octet-stream' :
                                  'application/pdf'),
-            aRequest, frontWindow, false);
+            aRequest, loadContext, false);
           this.extListener.onStartRequest(aRequest, aContext);
         },
         onStopRequest: function(aRequest, aContext, aStatusCode) {
@@ -1021,14 +1023,18 @@ PdfStreamConverter.prototype = {
     // Keep the URL the same so the browser sees it as the same.
     channel.originalURI = aRequest.URI;
     channel.loadGroup = aRequest.loadGroup;
+    channel.loadInfo.originAttributes = aRequest.loadInfo.originAttributes;
 
     // We can use resource principal when data is fetched by the chrome
+    // make sure we reuse the origin attributes from the request channel to keep
+    // isolation consistent.
     // e.g. useful for NoScript
     var ssm = Cc['@mozilla.org/scriptsecuritymanager;1']
                 .getService(Ci.nsIScriptSecurityManager);
     var uri = NetUtil.newURI(PDF_VIEWER_WEB_PAGE, null, null);
+    var attrs = aRequest.loadInfo.originAttributes;
     var resourcePrincipal;
-    resourcePrincipal = ssm.createCodebasePrincipal(uri, {});
+    resourcePrincipal = ssm.createCodebasePrincipal(uri, attrs);
     aRequest.owner = resourcePrincipal;
     channel.asyncOpen(proxy, aContext);
   },

browser/extensions/pdfjs/content/web/debugger.js

@@ -12,7 +12,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-/* globals PDFJS */
+/* globals pdfjsLib */
 
 'use strict';
 
@@ -307,8 +307,8 @@ var Stepper = (function StepperClosure() {
       this.table = table;
       if (!opMap) {
         opMap = Object.create(null);
-        for (var key in PDFJS.OPS) {
-          opMap[PDFJS.OPS[key]] = key;
+        for (var key in pdfjsLib.OPS) {
+          opMap[pdfjsLib.OPS[key]] = key;
         }
       }
     },
@@ -460,7 +460,7 @@ var Stats = (function Stats() {
     manager: null,
     init: function init() {
       this.panel.setAttribute('style', 'padding: 5px;');
-      PDFJS.enableStats = true;
+      pdfjsLib.PDFJS.enableStats = true;
     },
     enabled: false,
     active: false,

browser/extensions/pdfjs/content/web/viewer.css

@@ -191,12 +191,14 @@
 
 html {
   height: 100%;
+  width: 100%;
   /* Font size is needed to make the activity bar the correct size. */
   font-size: 10px;
 }
 
 body {
   height: 100%;
+  width: 100%;
   background-color: #404040;
   background-image: url(images/texture.png);
 }
@@ -1865,11 +1867,15 @@ html[dir='rtl'] #documentPropertiesOverlay .row > * {
   body[data-mozPrintCallback] #printContainer {
     display: block;
   }
+  #printContainer {
+    height: 100%;
+  }
   /* wrapper around (scaled) print canvas elements */
   #printContainer > div {
     position: relative;
     top: 0;
     left: 0;
+    height: 100%;
     overflow: hidden;
   }
   #printContainer canvas {

browser/themes/windows/browser-aero.css

@@ -368,13 +368,6 @@
     padding-right: 1px;
   }
 
-  /* Make the window draggable by glassed toolbars (bug 555081) */
-  #toolbar-menubar:not([autohide="true"]),
-  #TabsToolbar,
-  #navigator-toolbox > toolbar:not(#toolbar-menubar):not(#addon-bar):-moz-lwtheme {
-    -moz-binding: url("chrome://browser/content/customizableui/toolbar.xml#toolbar-drag");
-  }
-
   #appcontent:not(:-moz-lwtheme) {
     background-color: -moz-dialog;
   }
@@ -471,11 +464,6 @@
       background-color: rgb(215,228,242);
     }
 
-    #toolbar-menubar:not([autohide=true]):not(:-moz-lwtheme),
-    #TabsToolbar:not(:-moz-lwtheme) {
-      -moz-binding: url("chrome://browser/content/customizableui/toolbar.xml#toolbar-drag");
-    }
-
     /* Render a window top border for lwthemes: */
     #main-window[tabsintitlebar][sizemode="normal"] > #tab-view-deck > #browser-panel:-moz-lwtheme {
       background-image: linear-gradient(to bottom,

dom/bluetooth/bluedroid/BluetoothDaemonSocketInterface.cpp

@@ -222,7 +222,11 @@ public:
   {
     DaemonSocketPDU& pdu = GetPDU();
 
-    aArg1 = pdu.AcquireFd();
+    auto receiveFds = pdu.AcquireFds();
+    if (NS_WARN_IF(receiveFds.Length() == 0)) {
+      return NS_ERROR_ILLEGAL_VALUE;
+    }
+    aArg1 = receiveFds[0];
 
     if (NS_WARN_IF(aArg1 < 0)) {
       return NS_ERROR_ILLEGAL_VALUE;
@@ -279,7 +283,14 @@ BluetoothDaemonSocketModule::ConnectRsp(const DaemonSocketPDUHeader& aHeader,
                                         BluetoothSocketResultHandler* aRes)
 {
   /* the file descriptor is attached in the PDU's ancillary data */
-  int fd = aPDU.AcquireFd();
+  auto receiveFds = aPDU.AcquireFds();
+  if (receiveFds.Length() == 0) {
+    ErrorRunnable::Dispatch(aRes, &BluetoothSocketResultHandler::OnError,
+                            ConstantInitOp1<BluetoothStatus>(STATUS_FAIL));
+    return;
+  }
+  int fd = -1;
+  fd = receiveFds[0];
   if (fd < 0) {
     ErrorRunnable::Dispatch(aRes, &BluetoothSocketResultHandler::OnError,
                             ConstantInitOp1<BluetoothStatus>(STATUS_FAIL));

dom/nfc/gonk/NfcService.cpp

@@ -63,7 +63,7 @@ public:
   //
 
   void ReceiveSocketData(
-    int aIndex, nsAutoPtr<mozilla::ipc::UnixSocketBuffer>& aBuffer) override;
+    int aIndex, UniquePtr<mozilla::ipc::UnixSocketBuffer>& aBuffer) override;
 
   void OnConnectSuccess(int aIndex) override;
   void OnConnectError(int aIndex) override;
@@ -363,12 +363,12 @@ NfcConsumer::IsNfcServiceThread() const
 
 void
 NfcConsumer::ReceiveSocketData(
-  int aIndex, nsAutoPtr<mozilla::ipc::UnixSocketBuffer>& aBuffer)
+  int aIndex, UniquePtr<mozilla::ipc::UnixSocketBuffer>& aBuffer)
 {
   MOZ_ASSERT(IsNfcServiceThread());
   MOZ_ASSERT(aIndex == STREAM_SOCKET);
 
-  Receive(aBuffer);
+  Receive(aBuffer.get());
 }
 
 void

ipc/hal/DaemonSocketPDU.cpp

@@ -119,7 +119,7 @@ DaemonSocketPDU::Receive(int aFd)
   iv.iov_base = GetData(0);
   iv.iov_len = GetAvailableSpace();
 
-  uint8_t cmsgbuf[CMSG_SPACE(sizeof(int))];
+  uint8_t cmsgbuf[CMSG_SPACE(sizeof(int)* MAX_NFDS)];
 
   struct msghdr msg;
   memset(&msg, 0, sizeof(msg));
@@ -140,24 +140,33 @@ DaemonSocketPDU::Receive(int aFd)
 
   SetRange(0, res);
 
-  struct cmsghdr *chdr = CMSG_FIRSTHDR(&msg);
+  struct cmsghdr* chdr = CMSG_FIRSTHDR(&msg);
 
   for (; chdr; chdr = CMSG_NXTHDR(&msg, chdr)) {
     if (NS_WARN_IF(!CMSGHDR_CONTAINS_FD(chdr))) {
       continue;
     }
-    // Retrieve sent file descriptor. If multiple file descriptors
-    // have been sent, we close all but the final one.
-    mReceivedFd = *(static_cast<int*>(CMSG_DATA(chdr)));
+    // Retrieve sent file descriptors.
+    size_t fdCount = (chdr->cmsg_len - CMSG_ALIGN(sizeof(struct cmsghdr))) / sizeof(int);
+    for (size_t i = 0; i < fdCount; i++) {
+      int* receivedFd = static_cast<int*>(CMSG_DATA(chdr)) + i;
+      mReceivedFds.AppendElement(ScopedClose(*receivedFd));
+    }
   }
 
   return res;
 }
 
-int
-DaemonSocketPDU::AcquireFd()
+nsTArray<int>
+DaemonSocketPDU::AcquireFds()
 {
-  return mReceivedFd.forget();
+  // Forget all RAII object to avoid closing the fds.
+  nsTArray<int> fds;
+  for (auto& fd : mReceivedFds) {
+    fds.AppendElement(fd.forget());
+  }
+  mReceivedFds.Clear();
+  return fds;
 }
 
 nsresult

ipc/hal/DaemonSocketPDU.h

@@ -10,10 +10,12 @@
 #include "mozilla/FileUtils.h"
 #include "mozilla/ipc/SocketBase.h"
 #include "mozilla/ipc/DaemonSocketMessageHandlers.h"
+#include "nsTArray.h"
 
 namespace mozilla {
 namespace ipc {
 
+static const size_t MAX_NFDS = 16;
 class DaemonSocketIOConsumer;
 
 /**
@@ -72,7 +74,7 @@ public:
   ssize_t Send(int aFd) override;
   ssize_t Receive(int aFd) override;
 
-  int AcquireFd();
+  nsTArray<int> AcquireFds();
 
   nsresult UpdateHeader();
 
@@ -82,7 +84,7 @@ private:
 
   DaemonSocketIOConsumer* mConsumer;
   RefPtr<DaemonSocketResultHandler> mRes;
-  ScopedClose mReceivedFd;
+  nsTArray<ScopedClose> mReceivedFds;
 };
 
 }

ipc/ipdl/ipdl/lower.py

@@ -11,12 +11,6 @@ import ipdl.builtin
 from ipdl.cxx.ast import *
 from ipdl.type import Actor, ActorType, ProcessGraph, TypeVisitor, builtinHeaderIncludes
 
-# FIXME/cjones: the chromium Message logging code doesn't work on
-# gcc/POSIX, because it wprintf()s across the chromium/mozilla
-# boundary. one side builds with -fshort-wchar, the other doesn't.
-# this code will remain off until the chromium base lib is replaced
-EMIT_LOGGING_CODE = ('win32' == sys.platform)
-
 ##-----------------------------------------------------------------------------
 ## "Public" interface to lowering
 ##

ipc/keystore/KeyStore.cpp

@@ -882,7 +882,7 @@ KeyStore::SendData(const uint8_t *aData, int aLength)
 // |StreamSocketConsumer|, |ListenSocketConsumer|
 
 void
-KeyStore::ReceiveSocketData(int aIndex, nsAutoPtr<UnixSocketBuffer>& aMessage)
+KeyStore::ReceiveSocketData(int aIndex, UniquePtr<UnixSocketBuffer>& aMessage)
 {
   MOZ_ASSERT(NS_IsMainThread());
 
@@ -892,13 +892,13 @@ KeyStore::ReceiveSocketData(int aIndex, nsAutoPtr<UnixSocketBuffer>& aMessage)
          mHandlerInfo.state == STATE_PROCESSING) {
     switch (mHandlerInfo.state) {
       case STATE_IDLE:
-        result = ReadCommand(aMessage);
+        result = ReadCommand(aMessage.get());
         break;
       case STATE_READ_PARAM_LEN:
-        result = ReadLength(aMessage);
+        result = ReadLength(aMessage.get());
         break;
       case STATE_READ_PARAM_DATA:
-        result = ReadData(aMessage);
+        result = ReadData(aMessage.get());
         break;
       case STATE_PROCESSING:
         if (mHandlerInfo.command == 'g') {

ipc/keystore/KeyStore.h

@@ -124,7 +124,7 @@ private:
   //
 
   void ReceiveSocketData(int aIndex,
-                         nsAutoPtr<UnixSocketBuffer>& aMessage) override;
+                         UniquePtr<UnixSocketBuffer>& aMessage) override;
   void OnConnectSuccess(int aIndex) override;
   void OnConnectError(int aIndex) override;
   void OnDisconnect(int aIndex) override;

ipc/unixsocket/StreamSocket.cpp

@@ -227,7 +227,7 @@ public:
   }
 
 private:
-  nsAutoPtr<UnixSocketBuffer> mBuffer;
+  UniquePtr<UnixSocketBuffer> mBuffer;
 };
 
 void
@@ -366,7 +366,7 @@ StreamSocket::~StreamSocket()
 }
 
 void
-StreamSocket::ReceiveSocketData(nsAutoPtr<UnixSocketBuffer>& aBuffer)
+StreamSocket::ReceiveSocketData(UniquePtr<UnixSocketBuffer>& aBuffer)
 {
   mConsumer->ReceiveSocketData(mIndex, aBuffer);
 }

ipc/unixsocket/StreamSocket.h

@@ -34,7 +34,7 @@ public:
    *
    * @param aBuffer Data received from the socket.
    */
-  void ReceiveSocketData(nsAutoPtr<UnixSocketBuffer>& aBuffer);
+  void ReceiveSocketData(UniquePtr<UnixSocketBuffer>& aBuffer);
 
   /**
    * Starts a task on the socket that will try to connect to a socket in a

ipc/unixsocket/StreamSocketConsumer.h

@@ -7,7 +7,7 @@
 #ifndef mozilla_ipc_streamsocketconsumer_h
 #define mozilla_ipc_streamsocketconsumer_h
 
-#include "nsAutoPtr.h"
+#include "mozilla/UniquePtr.h"
 
 namespace mozilla {
 namespace ipc {
@@ -27,7 +27,7 @@ public:
    * @param aBuffer Data received from the socket.
    */
   virtual void ReceiveSocketData(int aIndex,
-                                 nsAutoPtr<UnixSocketBuffer>& aBuffer) = 0;
+                                 UniquePtr<UnixSocketBuffer>& aBuffer) = 0;
 
   /**
    * Callback for socket success. Consumer-thread only.

toolkit/content/xul.css

@@ -248,21 +248,21 @@ caption {
 titlebar,
 toolbar:not([nowindowdrag="true"]):not([customizing="true"]),
 statusbar:not([nowindowdrag="true"]),
+%endif
 windowdragbox {
   -moz-window-dragging: drag;
 }
 
 /* The list below is non-comprehensive and will probably need some tweaking. */
+toolbaritem,
 toolbarbutton,
 button,
 textbox,
-searchbar,
 tab,
 radio,
 splitter {
   -moz-window-dragging: no-drag;
 }
-%endif
 
 /******* toolbar *******/
 

toolkit/modules/WindowDraggingUtils.jsm

@@ -4,18 +4,18 @@
 
 Components.utils.import("resource://gre/modules/AppConstants.jsm");
 
-const USE_HITTEST = /^(win|macosx)/i.test(AppConstants.platform);
+const HAVE_CSS_WINDOW_DRAG_SUPPORT = ["win", "macosx"].includes(AppConstants.platform);
 
 this.EXPORTED_SYMBOLS = [ "WindowDraggingElement" ];
 
 this.WindowDraggingElement = function WindowDraggingElement(elem) {
   this._elem = elem;
   this._window = elem.ownerDocument.defaultView;
+  if (HAVE_CSS_WINDOW_DRAG_SUPPORT && !this.isPanel()) {
+    return;
+  }
 
-  if (USE_HITTEST && !this.isPanel())
-    this._elem.addEventListener("MozMouseHittest", this, false);
-  else
-    this._elem.addEventListener("mousedown", this, false);
+  this._elem.addEventListener("mousedown", this, false);
 };
 
 WindowDraggingElement.prototype = {
@@ -57,12 +57,6 @@ WindowDraggingElement.prototype = {
   },
   handleEvent: function(aEvent) {
     let isPanel = this.isPanel();
-    if (USE_HITTEST && !isPanel) {
-      if (this.shouldDrag(aEvent))
-        aEvent.preventDefault();
-      return;
-    }
-
     switch (aEvent.type) {
       case "mousedown":
         if (!this.shouldDrag(aEvent))

widget/nsIWidgetListener.cpp

@@ -54,6 +54,11 @@ nsIWidgetListener::SizeModeChanged(nsSizeMode aSizeMode)
 {
 }
 
+void
+nsIWidgetListener::UIResolutionChanged()
+{
+}
+
 void
 nsIWidgetListener::FullscreenChanged(bool aInFullscreen)
 {

widget/nsIWidgetListener.h

@@ -79,6 +79,12 @@ public:
    */
   virtual void SizeModeChanged(nsSizeMode aSizeMode);
 
+  /**
+   * Called when the DPI (device resolution scaling factor) is changed,
+   * such that UI elements may need to be rescaled.
+   */
+  virtual void UIResolutionChanged();
+
   /**
    * Called when the z-order of the window is changed. Returns true if the
    * notification was handled. aPlacement indicates the new z order. If

widget/windows/nsWindowBase.cpp

@@ -113,6 +113,7 @@ void nsWindowBase::ChangedDPI()
     if (presShell) {
       presShell->BackingScaleFactorChanged();
     }
+    mWidgetListener->UIResolutionChanged();
   }
 }
 

xpfe/appshell/nsWebShellWindow.cpp

@@ -377,6 +377,17 @@ nsWebShellWindow::SizeModeChanged(nsSizeMode sizeMode)
   // then need to be different.
 }
 
+void
+nsWebShellWindow::UIResolutionChanged()
+{
+  nsCOMPtr<nsPIDOMWindowOuter> ourWindow =
+    mDocShell ? mDocShell->GetWindow() : nullptr;
+  if (ourWindow) {
+    MOZ_ASSERT(ourWindow->IsOuterWindow());
+    ourWindow->DispatchCustomEvent(NS_LITERAL_STRING("resolutionchange"));
+  }
+}
+
 void
 nsWebShellWindow::FullscreenChanged(bool aInFullscreen)
 {

xpfe/appshell/nsWebShellWindow.h

@@ -56,6 +56,7 @@ public:
   virtual bool WindowResized(nsIWidget* aWidget, int32_t aWidth, int32_t aHeight) override;
   virtual bool RequestWindowClose(nsIWidget* aWidget) override;
   virtual void SizeModeChanged(nsSizeMode sizeMode) override;
+  virtual void UIResolutionChanged() override;
   virtual void FullscreenChanged(bool aInFullscreen) override;
   virtual void OSToolbarButtonPressed() override;
   virtual bool ZLevelChanged(bool aImmediate, nsWindowZ *aPlacement,