aura: Remove NotifyAncestorWindowTransformed in window observer.

ui/aura/window_observer.h

Index: ui/aura/window_observer.h
diff --git a/ui/aura/window_observer.h b/ui/aura/window_observer.h
index 15292fc513a80f3adcbab1b6572895fd618805c3..ea887a0603cc0dbebd858e3e72929b580fc2f973 100644
--- a/ui/aura/window_observer.h
+++ b/ui/aura/window_observer.h
@@ -88,10 +88,6 @@ class AURA_EXPORT WindowObserver {
   virtual void OnWindowTransforming(Window* window) {}
   virtual void OnWindowTransformed(Window* window) {}
 
-  // Invoked when SetTransform() is invoked on an ancestor of the window being
-  // observed (including the window itself).
-  virtual void OnAncestorWindowTransformed(Window* source, Window* window) {}
-
   // Invoked when |window|'s position among its siblings in the stacking order
   // has changed.
   virtual void OnWindowStackingChanged(Window* window) {}