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

- Bug 1123516 - Implement maplike/setlike in WebIDL parser; r=bz (5d62bcd93)
- Bug 1140324 - Remove __noSuchMethod__ handling from WebIDL parser and throw an exception instead. r=peterv (f7ea99339)
- Bug 1123516 - Implement maplike/setlike in WebIDL Codegen; r=b (0ca39b335)
- Bug 1183604, add some more assertions to help implementing new cycle collectable classes, r=mccr8 (1e66d29fe)
- Bug 1178665 - Part 1: Make Promise::DispatchToMicroTask public. r=khuey (b962e6006)
- Bug 1178665 - Part 2 - Adapt to latest Animation.finish procedure changes. r=bbirtles (33219fc0d)
- Bug 1178665 - Part 3: Make finish notifications asynchronously in most cases. r=bbirtles, r=smaug (144c0944a)
- Bug 1180770 part 1. Remove the unused ThrowNotEnoughArgsError. r=peterv (8bc1690f5)
- Bug 1180770 part 2. Remove the unused ifaceName/memberName arguments of ThrowMethodFailedWithDetails and rename it to ThrowMethodFailed. r=peterv (ee4900547)
- Bug 1135961. Implement subclassing of DOM objects. r=peterv (8e7e67b88)
- Bug 1170691 - part 1 - add the generating script's directory to sys.path in file_generate.py; r=glandium (dd1520952)
- Bug 1168409 - part 1 - avoid importing buildconfig in histogram_tools.py; r=gfritzsche (6a46dce23)
- Bug 1168409 - part 2 - avoiding importing usecounters in histogram_tools.py; r=gfritzsche (21a468303)
- Bug 1144397. Disallow using fill when dedent would do. r=peterv (544d4978d)
- Bug 1158806. Don't try to include stuff for a generated hasInstance hook if we have no interface object, since in that case we don't need the include. r=peterv (d280a1608)
- missing bit of Bug 1161627 - part 2 - machine-convert TemporaryRef<T> to already_AddRefed<T> (c51384311)
- Bug 1166910 followup: Add missing 'override' keyword to HTMLImageElement method GetImageReferrerPolicy. rs=ehsan (9e3dc8e6d)
- Bug 1174913 - remove unnecessary attribute parsing. r=bz (fdb769eda)
- Bug 1170680 - Do not add non-animated images to the visible list in response to UNLOCKED_DRAW. r=tn (a594883e8)
- Bug 1174923 - Stop delaying the document load event until images are decoded. r=tn a=kwierso (caee1b25f)
- Bug 968923 - part 3b - propagating use counters from SVG images into owning/parent documents; r=seth (234a41484)
- Bug 968923 - part 3a - add core DOM use counter functionality; r=smaug (98bb77358)
- Bug 968923 - part 3c - miscellaneous telemetry changes for use counters; r=gfritzsche (83adec291)
- Bug 968923 - part 4 - hook up use counters to WebIDL bindings; r=bz (8545e9a9b)
- Bug 771367 - Update test_animations_omta.html to support testing pseudo-elements. r=dbaron (4b2e5481b)
- Bug 1177563 - Test that we share agent rule processors across different documents. r=dbaron (d64146359)
- Bug 1181450 - Make GENERATED_FILES more visible during the build by printing their name when they are being generated. r=gps (b0c2166e8)
- Bug 1215526 - part 1 - pass dependencies file to file_generate.py; r=glandium (a14ea304a)
- Bug 1215526 - part 2 - write dependencies to file_generate.py's depfile; r=glandium (dc49ad380)

dom/base/nsDOMWindowUtils.cpp

@@ -101,6 +101,7 @@
 #include "nsIContentIterator.h"
 #include "nsIDOMStyleSheet.h"
 #include "nsIStyleSheet.h"
+#include "nsIStyleSheetService.h"
 #include "nsContentPermissionHelper.h"
 #include "nsNetUtil.h"
 
@@ -3520,6 +3521,7 @@ nsDOMWindowUtils::RequestCompositorProperty(const nsAString& property,
 NS_IMETHODIMP
 nsDOMWindowUtils::GetOMTAStyle(nsIDOMElement* aElement,
                                const nsAString& aProperty,
+                               const nsAString& aPseudoElement,
                                nsAString& aResult)
 {
   MOZ_RELEASE_ASSERT(nsContentUtils::IsCallerChrome());
@@ -3531,6 +3533,15 @@ nsDOMWindowUtils::GetOMTAStyle(nsIDOMElement* aElement,
 
   nsRefPtr<nsROCSSPrimitiveValue> cssValue = nullptr;
   nsIFrame* frame = element->GetPrimaryFrame();
+  if (frame && !aPseudoElement.IsEmpty()) {
+    if (aPseudoElement.EqualsLiteral("::before")) {
+      frame = nsLayoutUtils::GetBeforeFrame(frame);
+    } else if (aPseudoElement.EqualsLiteral("::after")) {
+      frame = nsLayoutUtils::GetAfterFrame(frame);
+    } else {
+      return NS_ERROR_INVALID_ARG;
+    }
+  }
   if (frame && nsLayoutUtils::AreAsyncAnimationsEnabled()) {
     if (aProperty.EqualsLiteral("opacity")) {
       Layer* layer =
@@ -3864,6 +3875,21 @@ nsDOMWindowUtils::LeaveChaosMode()
   return NS_OK;
 }
 
+NS_IMETHODIMP
+nsDOMWindowUtils::HasRuleProcessorUsedByMultipleStyleSets(uint32_t aSheetType,
+                                                          bool* aRetVal)
+{
+  MOZ_RELEASE_ASSERT(nsContentUtils::IsCallerChrome());
+
+  nsIPresShell* presShell = GetPresShell();
+  if (!presShell) {
+    return NS_ERROR_FAILURE;
+  }
+
+  return presShell->HasRuleProcessorUsedByMultipleStyleSets(aSheetType,
+                                                            aRetVal);
+}
+
 NS_INTERFACE_MAP_BEGIN(nsTranslationNodeList)
   NS_INTERFACE_MAP_ENTRY(nsISupports)
   NS_INTERFACE_MAP_ENTRY(nsITranslationNodeList)