Make the second click on the app shelf icon close the window-list bubble.

ash/shelf/shelf_view.h

Index: ash/shelf/shelf_view.h
diff --git a/ash/shelf/shelf_view.h b/ash/shelf/shelf_view.h
index 7aac1deb419093682c696464d7071cecf58eb44a..95f8039b52254b7b27967c8b8909cb8b31903c5c 100644
--- a/ash/shelf/shelf_view.h
+++ b/ash/shelf/shelf_view.h
@@ -435,6 +435,12 @@ class ASH_EXPORT ShelfView : public views::View,
   // True when ripped item from overflow bubble is entered into Shelf.
   bool dragged_off_from_overflow_to_shelf_;
 
+  // Record the position of each pointer down event.
+  gfx::Point pointer_pressed_position_;
+
+  // True if the pointer press position is the same with the previous one.
+  bool pressed_on_same_position_;
+
   DISALLOW_COPY_AND_ASSIGN(ShelfView);
 };