[cc] Plumb BeginFrameAcks through SurfaceManager to DisplayScheduler.

cc/surfaces/surface_manager.cc

Index: cc/surfaces/surface_manager.cc
diff --git a/cc/surfaces/surface_manager.cc b/cc/surfaces/surface_manager.cc
index cbdb78c5ea4a061887bcfc14fb2f627904fafd3f..52cb3ef5cac82aa748c402d39143c9468dc7cde7 100644
--- a/cc/surfaces/surface_manager.cc
+++ b/cc/surfaces/surface_manager.cc
@@ -498,6 +498,13 @@ void SurfaceManager::SurfaceDiscarded(Surface* surface) {
     dependency_tracker_->OnSurfaceDiscarded(surface);
 }
 
+void SurfaceManager::SurfaceProducerStateChanged(Surface* surface,
+                                                 Surface::ProducerState state) {
+  CHECK(thread_checker_.CalledOnValidThread());
+  for (auto& observer : observer_list_)
+    observer.OnSurfaceProducerStateChanged(surface->surface_id());
+}
+
 void SurfaceManager::UnregisterSurface(const SurfaceId& surface_id) {
   DCHECK(thread_checker_.CalledOnValidThread());
   SurfaceMap::iterator it = surface_map_.find(surface_id);