Implemented swipe to close in overview mode.

ash/wm/overview/transparent_activate_window_button_delegate.h

Index: ash/wm/overview/transparent_activate_window_button_delegate.h
diff --git a/ash/wm/overview/transparent_activate_window_button_delegate.h b/ash/wm/overview/transparent_activate_window_button_delegate.h
index c791a1894b5097ae91352ccf7b628e6342a3e088..9d4e9af7bd8103561e6c80181529c761c662247b 100644
--- a/ash/wm/overview/transparent_activate_window_button_delegate.h
+++ b/ash/wm/overview/transparent_activate_window_button_delegate.h
@@ -12,9 +12,20 @@ namespace ash {
 // 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() {}