Require the cursor to move a minimum distance after the mouse press before initiating a mouse drag

ash/shelf/shelf_view.h

 // Copyright (c) 2012 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_SHELF_SHELF_VIEW_H_
 #define ASH_SHELF_SHELF_VIEW_H_
 
 #include <utility>
 #include <vector>
 
@@ skipping 340 matching lines @@
   scoped_ptr<ShelfTooltipManager> tooltip_;
 
   // Pointer device that initiated the current drag operation. If there is no
   // current dragging operation, this is NONE.
   Pointer drag_pointer_;
 
   // The view being dragged. This is set immediately when the mouse is pressed.
   // |dragging_| is set only if the mouse is dragged far enough.
   views::View* drag_view_;
 
-  // X coordinate of the mouse down event in |drag_view_|s coordinates.
-  int drag_offset_;
+  // Position of the mouse down event in |drag_view_|'s coordinates.
+  gfx::Point drag_origin_;
 
   // Index |drag_view_| was initially at.
   int start_drag_index_;
 
   // Used for the context menu of a particular item.
   ShelfID context_menu_id_;
 
   scoped_ptr<views::FocusSearch> focus_search_;
 
   scoped_ptr<ui::MenuModel> list_menu_model_;
@@ skipping 68 matching lines @@
 
   // True when ripped item from overflow bubble is entered into Shelf.
   bool dragged_off_from_overflow_to_shelf_;
 
   DISALLOW_COPY_AND_ASSIGN(ShelfView);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SHELF_SHELF_VIEW_H_