[Mac]Implement ViewID support.

chrome/browser/cocoa/draggable_button.h

 // Copyright (c) 2010 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.
 
 #import <Cocoa/Cocoa.h>
+#import "chrome/browser/cocoa/button_with_viewid.h"
 
 // Class for buttons that can be drag sources. If the mouse is clicked and moved
 // more than a given distance, this class will call |-beginDrag:| instead of
 // |-performClick:|. Subclasses should override these two methods.
-@interface DraggableButton : NSButton {
+@interface DraggableButton : ButtonWithViewID {
  @private
   BOOL draggable_;     // Is this a draggable type of button?
 }
 
 // Enable or disable dragability for special buttons like "Other Bookmarks".
 @property (nonatomic) BOOL draggable;
 
 // Called when a drag should start. Subclasses must override this to do any
 // pasteboard manipulation and begin the drag, usually with
 // -dragImage:at:offset:event:.  Subclasses must call one of the blocking
 // -drag* methods of NSView when overriding this method.
 - (void)beginDrag:(NSEvent*)dragEvent;
 
 @end  // @interface DraggableButton
 
 @interface DraggableButton (Private)
 
 // Resets the draggable state of the button after dragging is finished.  This is
 // called by DraggableButton when the beginDrag call returns, it should not be
 // called by the subclass.
 - (void)endDrag;
 
 @end  // @interface DraggableButton(Private)