Mus+Ash: propagate Surface ID to parents

services/ui/public/cpp/window_observer.h

Index: services/ui/public/cpp/window_observer.h
diff --git a/services/ui/public/cpp/window_observer.h b/services/ui/public/cpp/window_observer.h
index a5c003be32873277113004988ccc890d6725487d..fb8a355e5dcac281869d711b5ee4abbe248f97ea 100644
--- a/services/ui/public/cpp/window_observer.h
+++ b/services/ui/public/cpp/window_observer.h
@@ -118,6 +118,13 @@ class WindowObserver {
   virtual void OnTransientChildRemoved(ui::Window* window,
                                        ui::Window* transient) {}
 
+  virtual void OnChildWindowSurfaceCreated(
+      Window* window,
+      const cc::SurfaceId& surface_id,
+      const cc::SurfaceSequence& surface_sequence,
+      const gfx::Size& frame_size,
+      float device_scale_factor) {}
+
   // The WindowManager has requested the window to close. If the observer
   // allows the close it should destroy the window as appropriate.
   virtual void OnRequestClose(Window* window) {}