[Chromecast] Limit number of concurrent audio and video decoders

chromecast/media/cma/backend/media_pipeline_backend_manager.h

Index: chromecast/media/cma/backend/media_pipeline_backend_manager.h
diff --git a/chromecast/media/cma/backend/media_pipeline_backend_manager.h b/chromecast/media/cma/backend/media_pipeline_backend_manager.h
index 54e6f205ad0e4d2cdfdbedb5c4fa01c2035ae031..d61621be4bc017552755e144bb3631acd011350f 100644
--- a/chromecast/media/cma/backend/media_pipeline_backend_manager.h
+++ b/chromecast/media/cma/backend/media_pipeline_backend_manager.h
@@ -49,6 +49,13 @@ class MediaPipelineBackendManager {
  private:
   friend class MediaPipelineBackendWrapper;
 
+  // Backend wrapper instances must use these APIs when allocating and releasing
+  // decoder objects, so we can enforce global limit on #concurrent decoders.
+  bool IncrementAudioDecoderCount();
+  bool IncrementVideoDecoderCount();
+  void DecrementAudioDecoderCount();
+  void DecrementVideoDecoderCount();
+
   // Internal clean up when a new media pipeline backend is destroyed.
   void OnMediaPipelineBackendDestroyed(const MediaPipelineBackend* backend);
 
@@ -59,6 +66,10 @@ class MediaPipelineBackendManager {
   // A vector that stores all of the existing media_pipeline_backends_.
   std::vector<MediaPipelineBackend*> media_pipeline_backends_;
 
+  // Total count of decoders created
+  int audio_decoder_count_;
+  int video_decoder_count_;
+
   // Volume multiplier for each type of audio streams.
   std::map<int, float> volume_by_stream_type_;