diff -r 000000000000 -r 6474c204b198 content/media/MediaShutdownManager.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/content/media/MediaShutdownManager.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,149 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* 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 "MediaShutdownManager.h"
+#include "nsContentUtils.h"
+#include "mozilla/StaticPtr.h"
+#include "MediaDecoder.h"
+#include "SharedThreadPool.h"
+#include "prlog.h"
+
+namespace mozilla {
+
+#ifdef PR_LOGGING
+extern PRLogModuleInfo* gMediaDecoderLog;
+#define DECODER_LOG(type, msg) PR_LOG(gMediaDecoderLog, type, msg)
+#else
+#define DECODER_LOG(type, msg)
+#endif
+
+NS_IMPL_ISUPPORTS(MediaShutdownManager, nsIObserver)
+
+MediaShutdownManager::MediaShutdownManager()
+  : mIsObservingShutdown(false),
+    mIsDoingXPCOMShutDown(false)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_COUNT_CTOR(MediaShutdownManager);
+}
+
+MediaShutdownManager::~MediaShutdownManager()
+{
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_COUNT_DTOR(MediaShutdownManager);
+}
+
+// Note that we don't use ClearOnShutdown() on this StaticRefPtr, as that
+// may interfere with our shutdown listener.
+StaticRefPtr<MediaShutdownManager> MediaShutdownManager::sInstance;
+
+MediaShutdownManager&
+MediaShutdownManager::Instance()
+{
+  MOZ_ASSERT(NS_IsMainThread());
+  if (!sInstance) {
+    sInstance = new MediaShutdownManager();
+  }
+  return *sInstance;
+}
+
+void
+MediaShutdownManager::EnsureCorrectShutdownObserverState()
+{
+  MOZ_ASSERT(!mIsDoingXPCOMShutDown);
+  bool needShutdownObserver = mDecoders.Count() > 0;
+  if (needShutdownObserver != mIsObservingShutdown) {
+    mIsObservingShutdown = needShutdownObserver;
+    if (mIsObservingShutdown) {
+      nsContentUtils::RegisterShutdownObserver(this);
+    } else {
+      nsContentUtils::UnregisterShutdownObserver(this);
+      // Clear our singleton reference. This will probably delete
+      // this instance, so don't deref |this| clearing sInstance.
+      sInstance = nullptr;
+    }
+  }
+}
+
+void
+MediaShutdownManager::Register(MediaDecoder* aDecoder)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+  // Don't call Register() after you've Unregistered() all the decoders,
+  // that's not going to work.
+  MOZ_ASSERT(!mDecoders.Contains(aDecoder));
+  mDecoders.PutEntry(aDecoder);
+  MOZ_ASSERT(mDecoders.Contains(aDecoder));
+  MOZ_ASSERT(mDecoders.Count() > 0);
+  EnsureCorrectShutdownObserverState();
+}
+
+void
+MediaShutdownManager::Unregister(MediaDecoder* aDecoder)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(mDecoders.Contains(aDecoder));
+  if (!mIsDoingXPCOMShutDown) {
+    mDecoders.RemoveEntry(aDecoder);
+    EnsureCorrectShutdownObserverState();
+  }
+}
+
+NS_IMETHODIMP
+MediaShutdownManager::Observe(nsISupports *aSubjet,
+                              const char *aTopic,
+                              const char16_t *someData)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+  if (strcmp(aTopic, NS_XPCOM_SHUTDOWN_OBSERVER_ID) == 0) {
+    Shutdown();
+  }
+  return NS_OK;
+}
+
+static PLDHashOperator
+ShutdownMediaDecoder(nsRefPtrHashKey<MediaDecoder>* aEntry, void*)
+{
+  aEntry->GetKey()->Shutdown();
+  return PL_DHASH_REMOVE;
+}
+
+void
+MediaShutdownManager::Shutdown()
+{
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(sInstance);
+
+  DECODER_LOG(PR_LOG_DEBUG, ("MediaShutdownManager::Shutdown() start..."));
+
+  // Mark that we're shutting down, so that Unregister(*) calls don't remove
+  // hashtable entries. If Unregsiter(*) was to remove from the hash table,
+  // the iterations over the hashtables below would be disrupted.
+  mIsDoingXPCOMShutDown = true;
+
+  // Iterate over the decoders and shut them down, and remove them from the
+  // hashtable.
+  mDecoders.EnumerateEntries(ShutdownMediaDecoder, nullptr);
+
+  // Ensure all media shared thread pools are shutdown. This joins with all
+  // threads in the state machine thread pool, the decoder thread pool, and
+  // any others.
+  SharedThreadPool::SpinUntilShutdown();
+
+  // Remove the MediaShutdownManager instance from the shutdown observer
+  // list.
+  nsContentUtils::UnregisterShutdownObserver(this);
+
+  // Clear the singleton instance. The only remaining reference should be the
+  // reference that the observer service used to call us with. The
+  // MediaShutdownManager will be deleted once the observer service cleans
+  // up after it finishes its notifications.
+  sInstance = nullptr;
+
+  DECODER_LOG(PR_LOG_DEBUG, ("MediaShutdownManager::Shutdown() end."));
+}
+
+} // namespace mozilla