Bug 1287350. Part 2 - Call WatchManager::Shutdown() to prevent notifications from watchables. r=jya

MozReview-Commit-ID: 79GojLNE4Gn

--HG--
extra : rebase_source : 888c389f0a99365da907a4dc56c8095cddfdbf55

dom/media/MediaDecoder.cpp

@@ -626,6 +626,9 @@ MediaDecoder::Shutdown()
 
   mShuttingDown = true;
 
+  // Unwatch all watch targets to prevent further notifications.
+  mWatchManager.Shutdown();
+
   mResourceCallback->Disconnect();
 
 #ifdef MOZ_EME
@@ -643,8 +646,6 @@ MediaDecoder::Shutdown()
     mOnSeekingStart.Disconnect();
     mOnMediaNotSeekable.Disconnect();
 
-    mWatchManager.Unwatch(mIsAudioDataAudible, &MediaDecoder::NotifyAudibleStateChanged);
-
     mDecoderStateMachine->BeginShutdown()
       ->Then(AbstractThread::MainThread(), __func__, this,
              &MediaDecoder::FinishShutdown,