[cc] Pass on BeginFrameAcks from CompositorEBFS through RWHVAura, DFH.

cc/ipc/traits_test_service.mojom

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 module cc.mojom;
 
 import "cc/ipc/begin_frame_args.mojom";
 import "cc/ipc/compositor_frame.mojom";
 import "cc/ipc/compositor_frame_metadata.mojom";
 import "cc/ipc/copy_output_request.mojom";
@@ skipping 11 matching lines @@
 import "cc/ipc/texture_mailbox.mojom";
 import "cc/ipc/transferable_resource.mojom";
 
 // All functions on this interface echo their arguments to test StructTraits
 // serialization and deserialization.
 interface TraitsTestService {
   [Sync]
   EchoBeginFrameArgs(BeginFrameArgs b) => (BeginFrameArgs pass);
 
   [Sync]
+  EchoBeginFrameAck(BeginFrameAck b) => (BeginFrameAck pass);
+
+  [Sync]
   EchoCompositorFrame(CompositorFrame c) => (CompositorFrame pass);
 
   [Sync]
   EchoCompositorFrameMetadata(CompositorFrameMetadata c) =>
       (CompositorFrameMetadata pass);
 
   [Sync]
   EchoCopyOutputRequest(CopyOutputRequest c) => (CopyOutputRequest pass);
 
   [Sync]
@@ skipping 27 matching lines @@
   EchoSurfaceSequence(SurfaceSequence s) => (SurfaceSequence pass);
 
   [Sync]
   EchoTextureMailbox(TextureMailbox t) =>
       (TextureMailbox pass);
 
   [Sync]
   EchoTransferableResource(TransferableResource t) =>
       (TransferableResource pass);
 };