Make using WebContentsUserData simpler.

chrome/browser/sessions/session_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/sessions/session_tab_helper.h"
 
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/sessions/session_service.h"
 #include "chrome/browser/sessions/session_service_factory.h"
 #include "chrome/browser/ui/tab_contents/tab_contents.h"
 #include "chrome/common/chrome_notification_types.h"
 #include "chrome/common/extensions/extension_messages.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/render_view_host.h"
 #include "content/public/browser/web_contents.h"
 
-int SessionTabHelper::kUserDataKey;
+DEFINE_WEB_CONTENTS_USER_DATA_KEY(SessionTabHelper)
 
 SessionTabHelper::SessionTabHelper(content::WebContents* contents)
     : content::WebContentsObserver(contents) {
 }
 
 SessionTabHelper::~SessionTabHelper() {
 }
 
 void SessionTabHelper::SetWindowID(const SessionID& id) {
   window_id_ = id;
@@ skipping 14 matching lines @@
 
 void SessionTabHelper::UserAgentOverrideSet(const std::string& user_agent) {
 #if defined(ENABLE_SESSION_SERVICE)
   Profile* profile =
       Profile::FromBrowserContext(web_contents()->GetBrowserContext());
   SessionService* session = SessionServiceFactory::GetForProfile(profile);
   if (session)
     session->SetTabUserAgentOverride(window_id(), session_id(), user_agent);
 #endif
 }