ARC Toast: Prevent onClosed event from being called multiple times

ash/system/toast/toast_overlay.h

Index: ash/system/toast/toast_overlay.h
diff --git a/ash/system/toast/toast_overlay.h b/ash/system/toast/toast_overlay.h
index 4bb3c5522c7540ef05917435db8d36dc5016f181..67f66d20834140a5552fef9cc4c4238a0f129ad0 100644
--- a/ash/system/toast/toast_overlay.h
+++ b/ash/system/toast/toast_overlay.h
@@ -44,23 +44,27 @@ class ASH_EXPORT ToastOverlay : public ui::LayerAnimationObserver {
  private:
   friend class ToastManagerTest;
 
+  void OnAnimationStopped();
+
   // Returns the current bounds of the overlay, which is based on visibility.
   gfx::Rect CalculateOverlayBounds();
 
   // gfx::LayerAnimationObserver overrides:
+  void OnLayerAnimationStarted(ui::LayerAnimationSequence* sequence) override;
   void OnLayerAnimationEnded(ui::LayerAnimationSequence* sequence) override;
   void OnLayerAnimationAborted(ui::LayerAnimationSequence* sequence) override;
   void OnLayerAnimationScheduled(ui::LayerAnimationSequence* sequence) override;
+  bool RequiresNotificationWhenAnimatorDestroyed() const override;
 
   views::Widget* widget_for_testing();
   void ClickDismissButtonForTesting(const ui::Event& event);
 
-  bool is_visible_ = false;
   Delegate* const delegate_;
   const std::string text_;
   scoped_ptr<views::Widget> overlay_widget_;
   scoped_ptr<ToastOverlayView> overlay_view_;
   gfx::Size widget_size_;
+  std::set<ui::LayerAnimationSequence*> inflight_animations_;
 
   DISALLOW_COPY_AND_ASSIGN(ToastOverlay);
 };