Hides ink ripple when a button drag is started

ui/views/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 UI_VIEWS_VIEW_H_
 #define UI_VIEWS_VIEW_H_
 
 #include <algorithm>
 #include <map>
 #include <set>
@@ skipping 918 matching lines @@
   virtual int OnDragUpdated(const ui::DropTargetEvent& event);
 
   // Invoked during a drag and drop session when the mouse exits the views, or
   // when the drag session was canceled and the mouse was over the view.
   virtual void OnDragExited();
 
   // Invoked during a drag and drop session when OnDragUpdated returns a valid
   // operation and the user release the mouse.
   virtual int OnPerformDrop(const ui::DropTargetEvent& event);
 
+  // Invoked from DoDrag when the drag starts. This implementation does
+  // nothing, and is intended for subclasses to do setup.
+  virtual void OnDragStarted(const ui::LocatedEvent& event);
+
   // Invoked from DoDrag after the drag completes. This implementation does
   // nothing, and is intended for subclasses to do cleanup.
   virtual void OnDragDone();
 
   // Returns true if the mouse was dragged enough to start a drag operation.
   // delta_x and y are the distance the mouse was dragged.
   static bool ExceededDragThreshold(const gfx::Vector2d& delta);
 
   // Accessibility -------------------------------------------------------------
 
@@ skipping 618 matching lines @@
   // Belongs to this view, but it's reference-counted on some platforms
   // so we can't use a scoped_ptr. It's dereferenced in the destructor.
   NativeViewAccessibility* native_view_accessibility_;
 
   DISALLOW_COPY_AND_ASSIGN(View);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_VIEW_H_