Bug 1096597 - Switch to buffering mode on WAITING_FOR_DATA. r=cpearce

dom/media/MediaDecoder.cpp

@@ -910,7 +910,6 @@ NS_IMETHODIMP MediaDecoder::Observe(nsISupports *aSubjet,
 MediaDecoder::Statistics
 MediaDecoder::GetStatistics()
 {
-  MOZ_ASSERT(NS_IsMainThread() || OnStateMachineThread());
   Statistics result;
 
   ReentrantMonitorAutoEnter mon(GetReentrantMonitor());

dom/media/MediaDecoderStateMachine.cpp

@@ -821,9 +821,15 @@ MediaDecoderStateMachine::OnNotDecoded(MediaData::Type aType,
     return;
   }
 
-  // If the decoder is waiting for data, there's nothing more to do after
-  // clearing the pending request.
+  // If the decoder is waiting for data, we need to make sure that the requests
+  // are cleared, which happened above. Additionally, if we're out of decoded
+  // samples, we need to switch to buffering mode.
   if (aReason == RequestSampleCallback::WAITING_FOR_DATA) {
+    bool outOfSamples = isAudio ? !AudioQueue().GetSize() : !VideoQueue().GetSize();
+    if (outOfSamples) {
+      StartBuffering();
+    }
+
     return;
   }