Make using WebContentsUserData simpler.

chrome/browser/ui/snapshot_tab_helper.cc

 // 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.
 
 #include "chrome/browser/ui/snapshot_tab_helper.h"
 
 #include "chrome/common/chrome_notification_types.h"
 #include "chrome/common/render_messages.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/web_contents.h"
 
 using content::WebContents;
 
-int SnapshotTabHelper::kUserDataKey;
+DEFINE_WEB_CONTENTS_USER_DATA_KEY(SnapshotTabHelper)
 
 SnapshotTabHelper::SnapshotTabHelper(WebContents* web_contents)
     : content::WebContentsObserver(web_contents) {
 }
 
 SnapshotTabHelper::~SnapshotTabHelper() {
 }
 
 void SnapshotTabHelper::CaptureSnapshot() {
   Send(new ChromeViewMsg_CaptureSnapshot(routing_id()));
@@ skipping 13 matching lines @@
 
 ////////////////////////////////////////////////////////////////////////////////
 // Internal helpers
 
 void SnapshotTabHelper::OnSnapshot(const SkBitmap& bitmap) {
   content::NotificationService::current()->Notify(
       chrome::NOTIFICATION_TAB_SNAPSHOT_TAKEN,
       content::Source<WebContents>(web_contents()),
       content::Details<const SkBitmap>(&bitmap));
 }