Add mailbox-based Mojo VideoFrame variant.

media/mojo/services/mojo_video_decoder_service.h

Index: media/mojo/services/mojo_video_decoder_service.h
diff --git a/media/mojo/services/mojo_video_decoder_service.h b/media/mojo/services/mojo_video_decoder_service.h
index cc65e05e0a4f7d5d5b4cf0d353b88bc62117238b..c03e1f0e9319184a10b8e559cf995de5262c7b8f 100644
--- a/media/mojo/services/mojo_video_decoder_service.h
+++ b/media/mojo/services/mojo_video_decoder_service.h
@@ -12,6 +12,10 @@
 #include "media/base/decode_status.h"
 #include "media/mojo/interfaces/video_decoder.mojom.h"
 
+namespace gpu {
+struct SyncToken;
+};
+
 namespace media {
 
 class DecoderBuffer;
@@ -37,6 +41,8 @@ class MojoVideoDecoderService : public mojom::VideoDecoder {
   void Decode(mojom::DecoderBufferPtr buffer,
               const DecodeCallback& callback) final;
   void Reset(const ResetCallback& callback) final;
+  void OnReleaseMailbox(const base::UnguessableToken& release_token,
+                        const gpu::SyncToken& release_sync_token) final;
 
  private:
   // Helper methods so that we can bind them with a weak pointer to avoid