Update BookmarkBarController to use non-deprecated dragging APIs.

chrome/browser/ui/cocoa/bookmarks/bookmark_button.h

 // Copyright (c) 2011 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>
 #include <vector>
 #import "chrome/browser/ui/cocoa/draggable_button.h"
 #import "chrome/browser/ui/cocoa/themed_window.h"
 #include "ui/base/window_open_disposition.h"
 
@@ skipping 172 matching lines @@
 - (void)removeButton:(NSInteger)buttonIndex animate:(BOOL)poof;
 
 // Determine the controller containing the button representing |node|, if any.
 - (id<BookmarkButtonControllerProtocol>)controllerForNode:
         (const bookmarks::BookmarkNode*)node;
 
 @end  // @protocol BookmarkButtonControllerProtocol
 
 
 // Class for bookmark bar buttons that can be drag sources.
-@interface BookmarkButton : DraggableButton<ThemedWindowDrawing> {

[Avi (use Gerrit), 2016/03/18 21:41:03]

Are we not implementing that interface any more? I thought this was a change of
the dragging code only.

[erikchen, 2016/03/18 22:20:35]

oops! Accidentally removed this line in a recent change set.

+@interface BookmarkButton : DraggableButton<NSDraggingSource> {
  @private
   IBOutlet NSObject<BookmarkButtonDelegate>* delegate_;  // Weak.
 
   // Saved pointer to the BWC for the browser window that contains this button.
   // Used to lock and release bar visibility during a drag.  The pointer is
   // saved because the bookmark button is no longer a part of a window at the
   // end of a drag operation (or, in fact, can be dragged to a completely
   // different window), so there is no way to retrieve the same BWC object after
   // a drag.
   BrowserWindowController* visibilityDelegate_;  // weak
@@ skipping 41 matching lines @@
 + (BookmarkButton*)draggedButton;
 
 
 @end  // @interface BookmarkButton
 
 
 @interface BookmarkButton(TestingAPI)
 - (void)beginDrag:(NSEvent*)event;
 @end