Refactors event dispatching of NativeViewport into its own interface

mojo/services/view_manager/display_manager.cc

Index: mojo/services/view_manager/display_manager.cc
diff --git a/mojo/services/view_manager/display_manager.cc b/mojo/services/view_manager/display_manager.cc
index 548817730d000204482a9c64a0edf7a2468776f1..e307fde1629a3af3956d534ed6b87ee6838d1dff 100644
--- a/mojo/services/view_manager/display_manager.cc
+++ b/mojo/services/view_manager/display_manager.cc
@@ -88,6 +88,10 @@ DisplayManager::DisplayManager(
   app_connection->ConnectToService("mojo:surfaces_service", &surfaces_service_);
   surfaces_service_->CreateSurfaceConnection(base::Bind(
       &DisplayManager::OnSurfaceConnectionCreated, weak_factory_.GetWeakPtr()));
+
+  NativeViewportEventDispatcherPtr event_dispatcher;
+  app_connection->ConnectToService(&event_dispatcher);
+  native_viewport_->SetEventDispatcher(event_dispatcher.Pass());
 }
 
 DisplayManager::~DisplayManager() {
@@ -157,12 +161,6 @@ void DisplayManager::OnSizeChanged(SizePtr size) {
   SchedulePaint(connection_manager_->root(), gfx::Rect(size_));
 }
 
-void DisplayManager::OnEvent(EventPtr event,
-                             const mojo::Callback<void()>& callback) {
-  connection_manager_->DispatchViewInputEventToDelegate(event.Pass());
-  callback.Run();
-}
-
 void DisplayManager::ReturnResources(Array<ReturnedResourcePtr> resources) {
   DCHECK_EQ(0u, resources.size());
 }