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

content/common/gpu/media/gpu_video_decode_accelerator.cc

Index: content/common/gpu/media/gpu_video_decode_accelerator.cc
diff --git a/content/common/gpu/media/gpu_video_decode_accelerator.cc b/content/common/gpu/media/gpu_video_decode_accelerator.cc
index 2bab173172258ee37150897fcf6ab5848ca0d954..b729141a83ff75c8fa7f5aba13adea211d6c6970 100644
--- a/content/common/gpu/media/gpu_video_decode_accelerator.cc
+++ b/content/common/gpu/media/gpu_video_decode_accelerator.cc
@@ -602,9 +602,9 @@ void GpuVideoDecodeAccelerator::OnReusePictureBuffer(
   video_decode_accelerator_->ReusePictureBuffer(picture_buffer_id);
 }
 
-void GpuVideoDecodeAccelerator::OnFlush() {
+void GpuVideoDecodeAccelerator::OnFlush(bool return_buffers) {
   DCHECK(video_decode_accelerator_);
-  video_decode_accelerator_->Flush();
+  video_decode_accelerator_->Flush(return_buffers);
 }
 
 void GpuVideoDecodeAccelerator::OnReset() {