[ash-md] Animates overview shield in and out

ash/common/wm/overview/window_selector_controller.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ASH_COMMON_WM_OVERVIEW_WINDOW_SELECTOR_CONTROLLER_H_
 #define ASH_COMMON_WM_OVERVIEW_WINDOW_SELECTOR_CONTROLLER_H_
 
 #include <list>
 #include <memory>
 #include <vector>
@@ skipping 26 matching lines @@
 
   // Returns true if window selection mode is active.
   bool IsSelecting();
 
   // Returns true if overview mode is restoring minimized windows so that they
   // are visible during overview mode.
   bool IsRestoringMinimizedWindows() const;
 
   // WindowSelectorDelegate:
   void OnSelectionEnded() override;
+  void AddDelayedAnimationObserver(
+      std::unique_ptr<DelayedAnimationObserver> animation) override;
+  void RemoveAndDestroyAnimationObserver(
+      DelayedAnimationObserver* animation) override;
 
  private:
   friend class WindowSelectorTest;
 
   // Dispatched when window selection begins.
   void OnSelectionStarted();
 
+  // Collection of DelayedAnimationObserver objects that own widgets that may be
+  // still animating after overview mode ends. If shell needs to shut down while
+  // those animations are in progress, the animations are shut down and the
+  // widgets destroyed.
+  std::vector<std::unique_ptr<DelayedAnimationObserver>> delayed_animations_;
   std::unique_ptr<WindowSelector> window_selector_;
   base::Time last_selection_time_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowSelectorController);
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_WM_OVERVIEW_WINDOW_SELECTOR_CONTROLLER_H_