Implement flushing in VTVideoDecodeAccelerator.

content/common/gpu/media/vt_video_decode_accelerator.h

Index: content/common/gpu/media/vt_video_decode_accelerator.h
diff --git a/content/common/gpu/media/vt_video_decode_accelerator.h b/content/common/gpu/media/vt_video_decode_accelerator.h
index 185d0fb1b77b039553a79feed89f3d5495f1163e..71748570a9fd9a8f1a78394a2548919fc03e9a52 100644
--- a/content/common/gpu/media/vt_video_decode_accelerator.h
+++ b/content/common/gpu/media/vt_video_decode_accelerator.h
@@ -64,16 +64,27 @@ class VTVideoDecodeAccelerator
     base::ScopedCFTypeRef<CVImageBufferRef> image_buffer;
   };
 
+  enum State {
+    // TODO(sandersd): Size changing state.
+    NORMAL,
+    FLUSHING,
+    RESETTING,
+    DESTROYING,
+  };
+
   // Methods for interacting with VideoToolbox. Run on |decoder_thread_|.
   void ConfigureDecoder(
       const std::vector<const uint8_t*>& nalu_data_ptrs,
       const std::vector<size_t>& nalu_data_sizes);
   void DecodeTask(const media::BitstreamBuffer);
+  void FlushTask();
 
   // Methods for interacting with |client_|. Run on |gpu_task_runner_|.
   void OutputTask(DecodedFrame frame);
   void SizeChangedTask(gfx::Size coded_size);
   void SendPictures();
+  void FlushStart(State state);
+  void FlushDone();
 
   //
   // GPU thread state.
@@ -81,6 +92,8 @@ class VTVideoDecodeAccelerator
   CGLContextObj cgl_context_;
   media::VideoDecodeAccelerator::Client* client_;
   gfx::Size texture_size_;
+  State state_;
+  int32_t frames_pending_decode_;
 
   // Texture IDs of pictures.
   // TODO(sandersd): A single map of structs holding picture data.