cc: Introduce BeginFrame sequence numbers and acknowledgements.

content/browser/compositor/mus_browser_compositor_output_surface.cc

Index: content/browser/compositor/mus_browser_compositor_output_surface.cc
diff --git a/content/browser/compositor/mus_browser_compositor_output_surface.cc b/content/browser/compositor/mus_browser_compositor_output_surface.cc
index ce3b426a44f88136c9d9d836638e37fd771ac7ae..1651429e46ec271123b57ca4a35829d7f5f98503 100644
--- a/content/browser/compositor/mus_browser_compositor_output_surface.cc
+++ b/content/browser/compositor/mus_browser_compositor_output_surface.cc
@@ -60,11 +60,18 @@ MusBrowserCompositorOutputSurface::MusBrowserCompositorOutputSurface(
 
 MusBrowserCompositorOutputSurface::~MusBrowserCompositorOutputSurface() {}
 
+cc::BeginFrameSource* MusBrowserCompositorOutputSurface::GetBeginFrameSource() {
+  return begin_frame_source_;
+}
+
 void MusBrowserCompositorOutputSurface::SwapBuffers(
     cc::OutputSurfaceFrame frame) {
   const gfx::Rect bounds = ui_window_ ? gfx::Rect(ui_window_->bounds().size())
                                       : gfx::Rect(window_->bounds().size());
   cc::CompositorFrame ui_frame;
+  ui_frame.metadata.begin_frame_source_id = frame.begin_frame_source_id;
+  ui_frame.metadata.begin_frame_number = frame.begin_frame_number;
+  ui_frame.metadata.latest_confirmed_frame = frame.latest_confirmed_frame;
   ui_frame.metadata.latency_info = std::move(frame.latency_info);
   // Reset latency_info to known empty state after moving contents.
   frame.latency_info.clear();
@@ -139,7 +146,9 @@ void MusBrowserCompositorOutputSurface::SwapBuffers(
 }
 
 void MusBrowserCompositorOutputSurface::SetBeginFrameSource(
-    cc::BeginFrameSource* source) {}
+    cc::BeginFrameSource* source) {
+  begin_frame_source_ = source;
+}
 
 void MusBrowserCompositorOutputSurface::ReclaimResources(
     const cc::ReturnedResourceArray& resources) {