Update desktop tree when Aura windows are removed.

ui/views/accessibility/ax_aura_obj_cache.h

Index: ui/views/accessibility/ax_aura_obj_cache.h
diff --git a/ui/views/accessibility/ax_aura_obj_cache.h b/ui/views/accessibility/ax_aura_obj_cache.h
index 763f8f99171fbcdb37cebf07ffb3a66e82258e4d..321b4162184468be149afe39bce2b52e1740b5b7 100644
--- a/ui/views/accessibility/ax_aura_obj_cache.h
+++ b/ui/views/accessibility/ax_aura_obj_cache.h
@@ -39,6 +39,11 @@ class VIEWS_EXPORT AXAuraObjCache
   // Get the single instance of this class.
   static AXAuraObjCache* GetInstance();
 
+  class Delegate {
+   public:
+    virtual void OnChildWindowRemoved(AXAuraObjWrapper* parent) = 0;
+  };
+
   // Get or create an entry in the cache based on an Aura view.
   AXAuraObjWrapper* GetOrCreate(View* view);
   AXAuraObjWrapper* GetOrCreate(Widget* widget);
@@ -56,7 +61,10 @@ class VIEWS_EXPORT AXAuraObjCache
   // Removes an entry from this cache based on an Aura view.
   void Remove(View* view);
   void Remove(Widget* widget);
-  void Remove(aura::Window* window);
+
+  // Removes |window| and optionally notifies delegate by sending an event on
+  // the |parent| if provided.
+  void Remove(aura::Window* window, aura::Window* parent);
 
   // Removes a view and all of its descendants from the cache.
   void RemoveViewSubtree(View* view);
@@ -76,6 +84,8 @@ class VIEWS_EXPORT AXAuraObjCache
   // Indicates if this object's currently being destroyed.
   bool is_destroying() { return is_destroying_; }
 
+  void SetDelegate(Delegate* delegate) { delegate_ = delegate; }
+
  private:
   friend struct base::DefaultSingletonTraits<AXAuraObjCache>;
 
@@ -117,6 +127,8 @@ class VIEWS_EXPORT AXAuraObjCache
   // True immediately when entering this object's destructor.
   bool is_destroying_;
 
+  Delegate* delegate_;
+
   DISALLOW_COPY_AND_ASSIGN(AXAuraObjCache);
 };