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

content/common/gpu/media/v4l2_video_decode_accelerator.h

Index: content/common/gpu/media/v4l2_video_decode_accelerator.h
diff --git a/content/common/gpu/media/v4l2_video_decode_accelerator.h b/content/common/gpu/media/v4l2_video_decode_accelerator.h
index 3d06665e344a27f0d490c34ed0dd7ae359b8529e..1c78293d351880b9bc3e83d3b88b0e323000b0f5 100644
--- a/content/common/gpu/media/v4l2_video_decode_accelerator.h
+++ b/content/common/gpu/media/v4l2_video_decode_accelerator.h
@@ -92,7 +92,7 @@ class CONTENT_EXPORT V4L2VideoDecodeAccelerator
   void AssignPictureBuffers(
       const std::vector<media::PictureBuffer>& buffers) override;
   void ReusePictureBuffer(int32_t picture_buffer_id) override;
-  void Flush() override;
+  void Flush(bool return_buffers) override;
   void Reset() override;
   void Destroy() override;
   bool CanDecodeOnIOThread() override;