[ash-md] Animates overview shield in and out

ash/common/wm/overview/window_selector_delegate.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_DELEGATE_H_
 #define ASH_COMMON_WM_OVERVIEW_WINDOW_SELECTOR_DELEGATE_H_
 
 #include "ash/ash_export.h"
 #include "base/compiler_specific.h"
 
-namespace aura {
-class Window;
-}
+namespace ash {
 
-namespace ash {
+class WindowSelectorDelegate;
+
+class ASH_EXPORT DelayedAnimationObserver {
+ public:
+  virtual ~DelayedAnimationObserver() {}
+
+  // Sets an |owner| that can be notified when the animation that |this|
+  // observes completes.
+  virtual void SetOwner(WindowSelectorDelegate* owner) = 0;
+
+  // Can be called by the |owner| to delete the owned widget. The |owner| is
+  // then responsible for deleting |this| instance of the
+  // DelayedAnimationObserver.
+  virtual void Shutdown() = 0;
+};
 
 // Implement this class to handle the selection event from WindowSelector.
 class ASH_EXPORT WindowSelectorDelegate {
  public:
   // Invoked if selection is ended.
   virtual void OnSelectionEnded() = 0;
 
+  // Passes ownership of |animation_observer| to |this| delegate.
+  virtual void AddDelayedAnimationObserver(
+      std::unique_ptr<DelayedAnimationObserver> animation_observer) = 0;
+
+  // Finds and erases |animation_observer| from the list deleting the widget
+  // owned by the |animation_observer|.
+  // This method should be called when a scheduled animation completes.
+  // If the animation completion callback is a result of a window getting
+  // destroyed then the DelayedAnimationObserver::Shutdown() should be called
+  // first before destroying the window.
+  virtual void RemoveAndDestroyAnimationObserver(
+      DelayedAnimationObserver* animation_observer) = 0;
+
  protected:
   virtual ~WindowSelectorDelegate() {}
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_WM_OVERVIEW_WINDOW_SELECTOR_DELEGATE_H_