Allow setting different hit test bounds overrides for mouse and touch

ash/wm/window_state_observer.h

Index: ash/wm/window_state_observer.h
diff --git a/ash/wm/window_state_observer.h b/ash/wm/window_state_observer.h
index 75008a8c1d8921fa8bb501366e804e4d21ffe0b9..7e18868a06cb44b11a4820ca799514ccb882bfe2 100644
--- a/ash/wm/window_state_observer.h
+++ b/ash/wm/window_state_observer.h
@@ -25,6 +25,10 @@ class ASH_EXPORT WindowStateObserver {
   // before the change.
   virtual void OnWindowShowTypeChanged(WindowState* window_state,
                                        WindowShowType old_type) {}
+
+  // Called when the fullscreen type of a fullscreen window changes.
+  virtual void OnWindowFullscreenTypeChanged(WindowState* window_state,
+                                             FullscreenType old_type) {}
 };
 
 }  // namespace wm