Bug 1109437 - Generalize GetBufferingWait to UseBufferingHeuristics. r=cpearce

dom/media/MediaDecoderReader.h

@@ -175,10 +175,11 @@ public:
 
   virtual int64_t ComputeStartTime(const VideoData* aVideo, const AudioData* aAudio);
 
-  // Wait this number of seconds when buffering, then leave and play
-  // as best as we can if the required amount of data hasn't been
-  // retrieved.
-  virtual uint32_t GetBufferingWait() { return 30; }
+  // The MediaDecoderStateMachine uses various heuristics that assume that
+  // raw media data is arriving sequentially from a network channel. This
+  // makes sense in the <video src="foo"> case, but not for more advanced use
+  // cases like MSE.
+  virtual bool UseBufferingHeuristics() { return true; }
 
   // Returns the number of bytes of memory allocated by structures/frames in
   // the video queue.

dom/media/MediaDecoderStateMachine.cpp

@@ -229,7 +229,7 @@ MediaDecoderStateMachine::MediaDecoderStateMachine(MediaDecoder* aDecoder,
   mAmpleVideoFrames =
     std::max<uint32_t>(Preferences::GetUint("media.video-queue.default-size", 10), 3);
 
-  mBufferingWait = mScheduler->IsRealTime() ? 0 : mReader->GetBufferingWait();
+  mBufferingWait = mScheduler->IsRealTime() ? 0 : 30;
   mLowDataThresholdUsecs = mScheduler->IsRealTime() ? 0 : LOW_DATA_THRESHOLD_USECS;
 
   mVideoPrerollFrames = mScheduler->IsRealTime() ? 0 : mAmpleVideoFrames / 2;

dom/media/mediasource/MediaSourceReader.h

@@ -78,11 +78,11 @@ public:
   // as chrome/blink and assumes that we always start at t=0.
   virtual int64_t ComputeStartTime(const VideoData* aVideo, const AudioData* aAudio) MOZ_OVERRIDE { return 0; }
 
-  // Buffering waits (in which we decline to present decoded frames because we
-  // "don't have enough") don't really make sense for MSE. The delay is
-  // essentially a streaming heuristic, but JS is supposed to take care of that
-  // in the MSE world. Avoid injecting inexplicable delays.
-  virtual uint32_t GetBufferingWait() { return 0; }
+  // Buffering heuristics don't make sense for MSE, because the arrival of data
+  // is at least partly controlled by javascript, and javascript does not expect
+  // us to sit on unplayed data just because it may not be enough to play
+  // through.
+  bool UseBufferingHeuristics() MOZ_OVERRIDE { return false; }
 
   bool IsMediaSeekable() { return true; }