Hook up BeginFrameSource to SurfaceFactoryClient via SurfaceManager

components/mus/ws/server_window_surface_manager.cc

Index: components/mus/ws/server_window_surface_manager.cc
diff --git a/components/mus/ws/server_window_surface_manager.cc b/components/mus/ws/server_window_surface_manager.cc
index 1699de41bc8006f97d94066f349ca176f0927731..1d90e17e427097529b00c1bc4f82a196d4fd6652 100644
--- a/components/mus/ws/server_window_surface_manager.cc
+++ b/components/mus/ws/server_window_surface_manager.cc
@@ -34,8 +34,16 @@ void ServerWindowSurfaceManager::CreateSurface(
     mojom::SurfaceType surface_type,
     mojo::InterfaceRequest<mojom::Surface> request,
     mojom::SurfaceClientPtr client) {
-  type_to_surface_map_[surface_type] = make_scoped_ptr(new ServerWindowSurface(
+  scoped_ptr<ServerWindowSurface> surface(new ServerWindowSurface(
       this, surface_type, std::move(request), std::move(client)));
+  if (!HasAnySurface()) {
+    // Only one SurfaceFactoryClient can be registered per surface id namespace,
+    // so register the first one.  Since all surfaces created by this manager
+    // represent the same window, the begin frame source can be shared by
+    // all surfaces created here.
+    surface->RegisterForBeginFrames();
+  }
+  type_to_surface_map_[surface_type] = std::move(surface);
 }
 
 ServerWindowSurface* ServerWindowSurfaceManager::GetDefaultSurface() {
@@ -52,10 +60,19 @@ ServerWindowSurface* ServerWindowSurfaceManager::GetSurfaceByType(
   return iter == type_to_surface_map_.end() ? nullptr : iter->second.get();
 }
 
-bool ServerWindowSurfaceManager::HasSurfaceOfType(mojom::SurfaceType type) {
+bool ServerWindowSurfaceManager::HasSurfaceOfType(
+    mojom::SurfaceType type) const {
   return type_to_surface_map_.count(type) > 0;
 }
 
+bool ServerWindowSurfaceManager::HasAnySurface() const {
+  return !GetDefaultSurface() && !GetUnderlaySurface();
+}
+
+SurfaceManager* ServerWindowSurfaceManager::GetSurfaceManager() {
+  return window()->delegate()->GetSurfacesState()->manager();
+}
+
 bool ServerWindowSurfaceManager::IsSurfaceReadyAndNonEmpty(
     mojom::SurfaceType type) const {
   auto iter = type_to_surface_map_.find(type);