Bug 938022. Part 2: Block captured MediaStream when the MediaDecoderStateMachine is not playing. r=cpearce

--HG--
extra : rebase_source : 01d887b3b5917b7c51a286d61feb10e7b2426d9a

content/media/MediaDecoder.cpp

@@ -199,7 +199,8 @@ MediaDecoder::DecodedStreamData::DecodedStreamData(MediaDecoder* aDecoder,
     mHaveSentFinishAudio(false),
     mHaveSentFinishVideo(false),
     mStream(aStream),
-    mHaveBlockedForPlayState(false)
+    mHaveBlockedForPlayState(false),
+    mHaveBlockedForStateMachineNotPlaying(false)
 {
   mStream->AddMainThreadListener(this);
 }
@@ -244,6 +245,29 @@ void MediaDecoder::DestroyDecodedStream()
   mDecodedStream = nullptr;
 }
 
+void MediaDecoder::UpdateStreamBlockingForStateMachinePlaying()
+{
+  GetReentrantMonitor().AssertCurrentThreadIn();
+  if (!mDecodedStream) {
+    return;
+  }
+  bool blockForStateMachineNotPlaying =
+    mDecoderStateMachine && !mDecoderStateMachine->IsPlaying() &&
+    mDecoderStateMachine->GetState() != MediaDecoderStateMachine::DECODER_STATE_COMPLETED;
+  if (blockForStateMachineNotPlaying != mDecodedStream->mHaveBlockedForStateMachineNotPlaying) {
+    mDecodedStream->mHaveBlockedForStateMachineNotPlaying = blockForStateMachineNotPlaying;
+    int32_t delta = blockForStateMachineNotPlaying ? 1 : -1;
+    if (NS_IsMainThread()) {
+      mDecodedStream->mStream->ChangeExplicitBlockerCount(delta);
+    } else {
+      nsCOMPtr<nsIRunnable> runnable =
+          NS_NewRunnableMethodWithArg<int32_t>(mDecodedStream->mStream.get(),
+              &MediaStream::ChangeExplicitBlockerCount, delta);
+      NS_DispatchToMainThread(runnable);
+    }
+  }
+}
+
 void MediaDecoder::RecreateDecodedStream(int64_t aStartTimeUSecs)
 {
   MOZ_ASSERT(NS_IsMainThread());
@@ -269,6 +293,7 @@ void MediaDecoder::RecreateDecodedStream(int64_t aStartTimeUSecs)
     }
     ConnectDecodedStreamToOutputStream(&os);
   }
+  UpdateStreamBlockingForStateMachinePlaying();
 
   mDecodedStream->mHaveBlockedForPlayState = mPlayState != PLAY_STATE_PLAYING;
   if (mDecodedStream->mHaveBlockedForPlayState) {

content/media/MediaDecoder.h

@@ -384,6 +384,9 @@ public:
     // True when we've explicitly blocked this stream because we're
     // not in PLAY_STATE_PLAYING. Used on the main thread only.
     bool mHaveBlockedForPlayState;
+    // We also have an explicit blocker on the stream when
+    // mDecoderStateMachine is non-null and MediaDecoderStateMachine is false.
+    bool mHaveBlockedForStateMachineNotPlaying;
 
     virtual void NotifyMainThreadStateChanged() MOZ_OVERRIDE;
   };
@@ -411,8 +414,14 @@ public:
    * Recreates mDecodedStream. Call this to create mDecodedStream at first,
    * and when seeking, to ensure a new stream is set up with fresh buffers.
    * aStartTimeUSecs is relative to the state machine's mStartTime.
+   * Decoder monitor must be held.
    */
   void RecreateDecodedStream(int64_t aStartTimeUSecs);
+  /**
+   * Call this when mDecoderStateMachine or mDecoderStateMachine->IsPlaying() changes.
+   * Decoder monitor must be held.
+   */
+  void UpdateStreamBlockingForStateMachinePlaying();
   /**
    * Called when the state of mDecodedStream as visible on the main thread
    * has changed. In particular we want to know when the stream has finished

content/media/MediaDecoderStateMachine.cpp

@@ -1316,6 +1316,7 @@ void MediaDecoderStateMachine::StopPlayback()
   // so it can pause audio playback.
   mDecoder->GetReentrantMonitor().NotifyAll();
   NS_ASSERTION(!IsPlaying(), "Should report not playing at end of StopPlayback()");
+  mDecoder->UpdateStreamBlockingForStateMachinePlaying();
 }
 
 void MediaDecoderStateMachine::StartPlayback()
@@ -1333,6 +1334,7 @@ void MediaDecoderStateMachine::StartPlayback()
     NS_WARNING("Failed to create audio thread");
   }
   mDecoder->GetReentrantMonitor().NotifyAll();
+  mDecoder->UpdateStreamBlockingForStateMachinePlaying();
 }
 
 void MediaDecoderStateMachine::UpdatePlaybackPositionInternal(int64_t aTime)

content/media/MediaDecoderStateMachine.h

@@ -345,6 +345,10 @@ public:
 
   void QueueMetadata(int64_t aPublishTime, int aChannels, int aRate, bool aHasAudio, bool aHasVideo, MetadataTags* aTags);
 
+  // Returns true if we're currently playing. The decoder monitor must
+  // be held.
+  bool IsPlaying();
+
 protected:
   virtual uint32_t GetAmpleVideoFrames() { return mAmpleVideoFrames; }
 
@@ -519,10 +523,6 @@ private:
 
   void StartDecodeMetadata();
 
-  // Returns true if we're currently playing. The decoder monitor must
-  // be held.
-  bool IsPlaying();
-
   // Returns the "media time". This is the absolute time which the media
   // playback has reached. i.e. this returns values in the range
   // [mStartTime, mEndTime], and mStartTime will not be 0 if the media does