Implemented swipe to close in overview mode.

ash/wm/overview/transparent_activate_window_button_delegate.h

 // Copyright 2014 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.
 // A delegate that
 
 #ifndef ASH_WM_OVERVIEW_TRANSPARENT_ACTIVATE_WINDOW_BUTTON_DELEGATE_H_
 #define ASH_WM_OVERVIEW_TRANSPARENT_ACTIVATE_WINDOW_BUTTON_DELEGATE_H_
 
 namespace ash {
 
 // A pure-virtual delegate that is used by the TransparentActivateWindowButton
 // to manipulate windows while in overview mode.
 class TransparentActivateWindowButtonDelegate {
  public:
+  // Called when a touch scroll event occurs. |drag_x| is an absolute pixel
+  // distance in the TransparentActivateWindowButton's local cooridnates.
+  virtual void Scroll(int delta_x) = 0;
+
+  // Called when a touch scroll event ends and the distance scrolled is less
+  // than the minimum close distance.
+  virtual void CancelScroll() = 0;
+
   // Called when the TransparentActivateWindowButton was selected.
   virtual void Select() = 0;
 
+  // Called when a TransparentActivateWindowButton close event occurs.
+  virtual void Close() = 0;
+
  protected:
   TransparentActivateWindowButtonDelegate() {}
   virtual ~TransparentActivateWindowButtonDelegate() {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(TransparentActivateWindowButtonDelegate);
 };
 
 }  // namespace ash
 
 #endif  // ASH_WM_OVERVIEW_TRANSPARENT_ACTIVATE_WINDOW_BUTTON_DELEGATE_H_