Add an additional VDA::Flush() mode to return all allocated buffers.

content/common/gpu/media/gpu_video_decode_accelerator.h

Index: content/common/gpu/media/gpu_video_decode_accelerator.h
diff --git a/content/common/gpu/media/gpu_video_decode_accelerator.h b/content/common/gpu/media/gpu_video_decode_accelerator.h
index 541271f3451562180f9f9b45e92c96de68f46799..3f175e910a84ad1d17f089268560069b5a7f870d 100644
--- a/content/common/gpu/media/gpu_video_decode_accelerator.h
+++ b/content/common/gpu/media/gpu_video_decode_accelerator.h
@@ -111,7 +111,7 @@ class GpuVideoDecodeAccelerator
   void OnAssignPictureBuffers(const std::vector<int32_t>& buffer_ids,
                               const std::vector<uint32_t>& texture_ids);
   void OnReusePictureBuffer(int32_t picture_buffer_id);
-  void OnFlush();
+  void OnFlush(bool return_buffers);
   void OnReset();
   void OnDestroy();