Remove CompositorObserver::OnCompositingEnded()

ui/compositor/compositor.cc

Index: ui/compositor/compositor.cc
diff --git a/ui/compositor/compositor.cc b/ui/compositor/compositor.cc
index 81a934550879bc91ea2e3d17bc273a65b206dbe4..212984fe2913e1db4005e4d3e55dcc507da2255a 100644
--- a/ui/compositor/compositor.cc
+++ b/ui/compositor/compositor.cc
@@ -525,15 +525,12 @@ void Compositor::DidFailToInitializeCompositorFrameSink() {
 
 void Compositor::DidCommit() {
   DCHECK(!IsLocked());
+  ++committed_frame_number_;
   for (auto& observer : observer_list_)
     observer.OnCompositingDidCommit(this);
 }
 
-void Compositor::DidReceiveCompositorFrameAck() {
-  ++committed_frame_number_;
-  for (auto& observer : observer_list_)
-    observer.OnCompositingEnded(this);
-}
+void Compositor::DidReceiveCompositorFrameAck() {}
 
 void Compositor::DidSubmitCompositorFrame() {
   base::TimeTicks start_time = base::TimeTicks::Now();