cc: Introduce BeginFrame sequence numbers and acknowledgements.

components/exo/surface.cc

Index: components/exo/surface.cc
diff --git a/components/exo/surface.cc b/components/exo/surface.cc
index d2419a5b64bc41a7e3ad84c24a9f16e80ddad2c3..48567f6279c54802c6cec4644b705c25fd0ba380 100644
--- a/components/exo/surface.cc
+++ b/components/exo/surface.cc
@@ -454,6 +454,12 @@ void Surface::Commit() {
     CheckIfSurfaceHierarchyNeedsCommitToNewSurfaces();
     CommitSurfaceHierarchy();
   }
+
+  cc::BeginFrameAck ack(last_begin_frame_args_.source_id,
+                        last_begin_frame_args_.sequence_number, true,
+                        last_begin_frame_args_.sequence_number, 0);
+  if (begin_frame_source_)
+    begin_frame_source_->DidFinishFrame(this, ack);
 }
 
 void Surface::CommitSurfaceHierarchy() {
@@ -647,11 +653,11 @@ void Surface::OnWindowRemovingFromRootWindow(aura::Window* window,
 }
 
 void Surface::OnBeginFrame(const cc::BeginFrameArgs& args) {
+  last_begin_frame_args_ = args;
   while (!active_frame_callbacks_.empty()) {
     active_frame_callbacks_.front().Run(args.frame_time);
     active_frame_callbacks_.pop_front();
   }
-  last_begin_frame_args_ = args;
 }
 
 const cc::BeginFrameArgs& Surface::LastUsedBeginFrameArgs() const {