Explicitly declare a method in WebContentsViewCocoa.

content/browser/web_contents/web_contents_view_mac.mm

 // 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.
 
 #import <Carbon/Carbon.h>
 
 #import "content/browser/web_contents/web_contents_view_mac.h"
 
 #include <string>
 
@@ skipping 507 matching lines @@
               dropData:&dropData
                  image:image
                 offset:offset
             pasteboard:[NSPasteboard pasteboardWithName:NSDragPboard]
      dragOperationMask:operationMask]);
   [dragSource_ startDrag];
 }
 
 // NSDraggingSource methods
 
-// Returns what kind of drag operations are available. This is a required
-// method for NSDraggingSource.
 - (NSDragOperation)draggingSourceOperationMaskForLocal:(BOOL)isLocal {
   if (dragSource_)
     return [dragSource_ draggingSourceOperationMaskForLocal:isLocal];
   // No web drag source - this is the case for dragging a file from the
   // downloads manager. Default to copy operation. Note: It is desirable to
   // allow the user to either move or copy, but this requires additional
   // plumbing to update the download item's path once its moved.
   return NSDragOperationCopy;
 }
 
@@ skipping 141 matching lines @@
 
 - (void)viewDidHide {
   [self updateWebContentsVisibility];
 }
 
 - (void)viewDidUnhide {
   [self updateWebContentsVisibility];
 }
 
 @end