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

- Bug 1218706 - Make 'unicode-bidi: isolate' the default for elements with a dir attribute. r=dbaron,jfkthame (037a5aaf57)
- Bug 743198 part 7 - Add :fullscreen pseudo class. r=heycam (05eb82ccc9)
- missing bits of  Bug 1242904 - Update Brotli t (f4f569d859)
- Bug 1235298 - Annotate intentional switch fallthroughs to suppress -Wimplicit-fallthrough warnings in netwerk/. r=mcmanus (c4ae414769)
- Bug 1244841 - Don't measure SharedArrayBuffer objects multiple times. r=lth. (e9b665dc82)
- Bug 234031 - broken parsing of xlen in gzip rfc 1952 r=mcmanus (c905b50417)
- Bug 1239605 - filter insertions into the global object. r=jandem (35520bc5c8)
- Bug 1248681 - Warn if the result of putWrapper goes unused; r=sfink (8051888ef8)
- Bug 1246293 - Fix a typo in DefineSelfHostedProperty; r=till (5e05a76b2a)
- Bug 1243808 - Allow modules to be compiled off main thread r=shu (51e5adca0a)
- Bug 1241767 - avoid default-only switch to placate MSVC. r=bbouvier (392aa8eda0)
- Bug 1239710 - Use CountingSort for Uint8Array and Int8Array; r=mrrrgn (6f394ab442)
- Bug 1246860 - Preserve holes when sorting arrays with a custom comparator. r=till (725b091e55)
- Bug 1247283 - Improve self-hosted Array.sort performance; r=till (ab1f3ddb74)
- Bug 1248717 - Don't initialize variables in a for head with var, then use them later. r=jorendorff (87a77f9623)
- Bug 1242196 - Use RadixSort for typed arrays. r=mrrrgn (a280ea097d)
- Bug 1246927 - Fix OOM handling in usages of GlobalObject::maybeGetIntrinsicValue. r=arai (f7f3761c45)
- Bug 1248405 - Recover from JSObject::getGroup OOM in CanOptimizeForDenseStorage. r=jandem (68ea32c044)
- Bug 1225905 - create a mozharness script that manages each beet mover task logic, NPOTB DONTBUILD r=rail (076f25536f)
- Bug 1246074 - add partials template config for mozharness beetmover, DONTBUILD r=rail (2e42c78d92)
- Bug 1246074 - add partials mozharness beetmover, custom tc artifact location, DONTBUILD NPOTB r=rail (c74fe0755a)
- Bug 1210538 - Add antivirus checks to release promotion graph a=rail (56de774389)
- Bug 1238610 - Restore compartment debug mode flags if adding a debuggee global fails r=jimb (f8a9a1fa85)
- Bug 1243851 - Treat enter as shift+enter if input is valid but incomplete; r=fitzgen, bgrins (f27c959bc0)
- Bug 1238610 - Fix implicit constructor errors r=me (6f26f92763)
- Bug 1242111 - Handle OOM in UpdateExecutionObservabilityOfScriptsInZone. (r=jimb) (91b125725f)
- Bug 1240503 - Skip the initial block scope when unwinding scopes due to an exception that's thrown in the prologue before the scope chain is properly initialized for a script that starts with a block scope. (r=jorendorff) (0247fc8848)
- Bug 1242111 - Fix references to oomTest. (r=me) (a9dc13a648)
- Bug 1240546 - Handle OOM in updateObservesAllExecutionOnDebuggees. (r=jimb) (5d7e3a49f4)
- Bug 1245961 - Throw a TypeError if less than one argument is supplied to isCompilableUnit;r=fitzgen (f896abb042)
- Bug 1240803 - Handle OOM in replaceFrameGuts. (r=jimb) (2d43384c72)
- Bug 1248094 - Simplify PCLocationMap with GCHashMap; r=fitzgen (b28d983bbd)
- we don't care much abut 68k sadly (51c50300c5)
- Bug 1233786 - JSScript::initScriptCounts should report OOMs. r=bhackett (eb42f7b8c1)
- Bug 1233178 - Move ScriptCounts allocation outside the HashMap. r=bhackett (c3fa6d487c)
- Bug 1141579 - Synchronize access to warmUpCount; r=jandem (a5b72cdf94)
- Bug 1203696: Improve comments about lazily-initialized member of js::LazyScript. r=shu (caa895612d)
- Bug 1221992 - Fix test using GetMostRecentWindow from the child process. r=smaug (07affe8195)
- Bug 1235636 - rewrite PCToLineNumber; r=fitzgen (9dc9ff013e)
- Bug 1232100 - "Check charsWritten in non-debug builds.". r=jcoppeard (fc5a64e621)
- last bit of  Bug 1197932 (86277af34e)
- Bug 1067049 - Implement arguments[@@iterator]. r=evilpie (543e513269)
- Bug 1248930 - Use Int32Value in ArrayBufferObject::BYTE_LENGTH_SLOT. r=lth (71e3a9ee51)
- Bug 1113685 - Report the right name when calling selfhosted functions on incompatible objects. r=till (51f68d4f8d)
- some symbol cleanup (83fca10034)
- Bug 1165011 - Remove Symbol_isRegExp. r=jorendorff (46a2d293cc)
- Bug 1122900: Make libyuv compile with MSVC 2015, r=rjesup. (9e147c7ba7)
- bug 1241453 - clean up GetAccessibleWrap() r=davidb (01e37c5012)
- Bug 1243331 - Prevent G_DEFINE_TYPE_EXTENDED macro from producing a fatal warning, r=tbsaunde (8bf031c4b9)
- Bug 1232527 - Call into WMF PDM to determine if WMF can decode instead of using GMPVideoDecoderTrialCreator. r=jwwang (7d2b1f16f1)
- Bug 1229475 - Fix gen-sources for libopus 1.1.1. r=cpearce (1e5a768d94)
- Bug 1229475 - Update libopus to 1.1.1 release. r=jmspeex (0b73488ab3)
- Bug 1139087 - Add moz.build bugzilla metadata for codecs. r=kinetik,gps (3d906f8f5a)
- Bug 1229475 - libopus: Patch out asm flags for run_analysis. r=jmspeex (bfa15edac1)
- Bug 1229475 - Fix unified build. r=cpearce (bbeda94cfc)
- Bug 1239078 - Update libopus to 1.1.2 release. r=kinetik (9990b00867)
- Bug 1239078 - Bump libopus update script for 1.1.2. r=kinetik (eecd46d3d3)
- bug 1230377 - part 1/2: ensure nsKeyObject releases NSS resources on shutdown r=jcj (9ceefecbea)
- bug 1230377 - part 2/2: simplify nsIKeyObject and nsIKeyObjectFactory r=jcj (1297d168b7)
- bug 1239609 - audit nsNSSShutDownObject destructors for correctness r=Cykesiopka,sworkman (c78404e52a)
- Bug 1246263 - fix unified build pollution r=valentin (f8db2c45cf)
- Bug 1214981 - Disable output stream buffering. r=keeler (d9e7a1b863)
- bug 1240173 - improve nsIX509Cert.dbKey r=Cykesiopka (0c0fc8e8a3)
- Bug 1238042 - Extract a helper function to check if a JSObject is a global with a particular about: URI. r=ehsan (d065854725)
- Bug 1244118 - Shutdown threadpool when xpcom-shutdown-threads happened. r=roc (e6ef2768b6)
- Bug 1201685 - Limit the number of indexedDB open() calls in IndexedDBHelper r=gwagner (a4fc80fca2)
- Bug 1244049 - Part 3: Replace the type of nsCSSSelector::mPseudoType. r=dbaron (c817ee6145)
- Bug 1244049 - Part 4: Define CSSPseudoElementTypeBase. r=dbaron (94dab59375)
- Bug 1246846 (part 1) - Avoid nsTHashtable::RawRemoveEntry() in dom/.  r=bz. (5371e478da)
- Bug 1246846 (part 2) - Avoid nsTHashtable::RawRemoveEntry() in nsPermissionManager. r=mconnor. (d7a1143ed1)
- Bug 1246846 (part 3) - Avoid nsTHashtable::RawRemoveEntry() in gfxFontconfigUtils. r=jfkthame. (d23259ca8e)
- Bug 1246846 (part 4) - Avoid nsTHashtable::RawRemoveEntry() in FramePropertyTable. r=roc. (7de416abfa)
- Bug 1238404 - Use 'using' directive instead of having separate Dispatch impl in subclasses of nsIEventTarget. r=froydnj (43028ed3b3)
- Bug 938699 - Remove FindElementWithViewId from nsIDOMWindowUtils.idl and nsDOMWindowUtils.cpp. r=kats (b49d2b5e6a)
- missing bit of Bug 1210294 - Remove the release-mode IsCallerChrome assertions (a555243280)

dom/base/ImageEncoder.cpp

@@ -5,7 +5,6 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "ImageEncoder.h"
-#include "mozilla/ClearOnShutdown.h"
 #include "mozilla/dom/CanvasRenderingContext2D.h"
 #include "mozilla/gfx/2D.h"
 #include "mozilla/gfx/DataSurfaceHelpers.h"
@@ -496,6 +495,38 @@ ImageEncoder::GetImageEncoder(nsAString& aType)
   return encoder.forget();
 }
 
+class EncoderThreadPoolTerminator final : public nsIObserver
+{
+  public:
+    NS_DECL_ISUPPORTS
+
+    NS_IMETHODIMP Observe(nsISupports *, const char *topic, const char16_t *) override
+    {
+      NS_ASSERTION(!strcmp(topic, "xpcom-shutdown-threads"),
+                   "Unexpected topic");
+      if (ImageEncoder::sThreadPool) {
+        ImageEncoder::sThreadPool->Shutdown();
+        ImageEncoder::sThreadPool = nullptr;
+      }
+      return NS_OK;
+    }
+  private:
+    ~EncoderThreadPoolTerminator() {}
+};
+
+NS_IMPL_ISUPPORTS(EncoderThreadPoolTerminator, nsIObserver)
+
+static void
+RegisterEncoderThreadPoolTerminatorObserver()
+{
+  MOZ_ASSERT(NS_IsMainThread());
+  nsCOMPtr<nsIObserverService> os = mozilla::services::GetObserverService();
+  NS_ASSERTION(os, "do_GetService failed");
+  os->AddObserver(new EncoderThreadPoolTerminator(),
+                  "xpcom-shutdown-threads",
+                  false);
+}
+
 /* static */
 nsresult
 ImageEncoder::EnsureThreadPool()
@@ -503,12 +534,13 @@ ImageEncoder::EnsureThreadPool()
   if (!sThreadPool) {
     nsCOMPtr<nsIThreadPool> threadPool = do_CreateInstance(NS_THREADPOOL_CONTRACTID);
     sThreadPool = threadPool;
+
     if (!NS_IsMainThread()) {
       NS_DispatchToMainThread(NS_NewRunnableFunction([]() -> void {
-        ClearOnShutdown(&sThreadPool);
+        RegisterEncoderThreadPoolTerminatorObserver();
       }));
     } else {
-      ClearOnShutdown(&sThreadPool);
+      RegisterEncoderThreadPoolTerminatorObserver();
     }
 
     const uint32_t kThreadLimit = 2;