[cc] Fix CompositorFrameSinkSupport BeginFrameAck interface.

content/browser/compositor/mus_browser_compositor_output_surface.cc

 // 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.
 
 #include "content/browser/compositor/mus_browser_compositor_output_surface.h"
 
 #include <utility>
 
 #include "cc/output/compositor_frame.h"
 #include "cc/output/output_surface_frame.h"
@@ skipping 35 matching lines @@
 cc::BeginFrameSource* MusBrowserCompositorOutputSurface::GetBeginFrameSource() {
   return begin_frame_source_;
 }
 
 void MusBrowserCompositorOutputSurface::SwapBuffers(
     cc::OutputSurfaceFrame frame) {
   cc::CompositorFrame ui_frame;
   ui_frame.metadata.device_scale_factor =
       ui::GetScaleFactorForNativeView(window_);
   ui_frame.metadata.latency_info = std::move(frame.latency_info);
+  // TODO(eseckler): Pass on BeginFrameAck from browser compositor via |frame|.
+  ui_frame.metadata.begin_frame_ack =
+      cc::BeginFrameAck(cc::BeginFrameArgs::kManualSourceId,
+                        cc::BeginFrameArgs::kStartingFrameNumber,
+                        cc::BeginFrameArgs::kStartingFrameNumber, 0, true);
   // Reset latency_info to known empty state after moving contents.
   frame.latency_info.clear();
   const int render_pass_id = 1;
   const gfx::Rect bounds_in_dip = gfx::Rect(window_->bounds().size());
   const gfx::Rect bounds_in_pixels = gfx::ConvertRectToPixel(
       ui_frame.metadata.device_scale_factor, bounds_in_dip);
   std::unique_ptr<cc::RenderPass> pass = cc::RenderPass::Create();
   pass->SetNew(render_pass_id, bounds_in_pixels, bounds_in_pixels,
                gfx::Transform());
   // The SharedQuadState is owned by the SharedQuadStateList
@@ skipping 115 matching lines @@
 
 const gpu::Mailbox& MusBrowserCompositorOutputSurface::GetMailboxFromResourceId(
     uint32_t id) {
   DCHECK_LT(id, mailboxes_.size());
   DCHECK(std::find(free_resource_ids_.begin(), free_resource_ids_.end(), id) ==
          free_resource_ids_.end());
   return mailboxes_[id];
 }
 
 }  // namespace content