Make using WebContentsUserData simpler.

chrome/browser/ui/sad_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/sad_tab_helper.h"
 
 #include "base/logging.h"
 #include "chrome/browser/browser_shutdown.h"
 #include "chrome/browser/ui/sad_tab_types.h"
 #include "content/public/browser/notification_source.h"
 #include "content/public/browser/notification_types.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/browser/web_contents_view.h"
 
 #if defined(OS_MACOSX)
 #include "chrome/browser/ui/cocoa/tab_contents/sad_tab_controller.h"
 #elif defined(TOOLKIT_VIEWS)
 #include "chrome/browser/ui/views/sad_tab_view.h"
 #include "ui/views/widget/widget.h"
 #elif defined(TOOLKIT_GTK)
 #include <gtk/gtk.h>
 
 #include "chrome/browser/ui/gtk/sad_tab_gtk.h"
 #include "chrome/browser/ui/gtk/tab_contents/chrome_web_contents_view_delegate_gtk.h"
 #endif
 
-int SadTabHelper::kUserDataKey;
+DEFINE_WEB_CONTENTS_USER_DATA_KEY(SadTabHelper)
 
 SadTabHelper::SadTabHelper(content::WebContents* web_contents)
     : content::WebContentsObserver(web_contents) {
   registrar_.Add(this, content::NOTIFICATION_WEB_CONTENTS_CONNECTED,
                  content::Source<content::WebContents>(web_contents));
 }
 
 SadTabHelper::~SadTabHelper() {
 }
 
@@ skipping 89 matching lines @@
   sad_tab_.reset(new SadTabGtk(web_contents(), kind));
   GtkWidget* expanded_container =
       ChromeWebContentsViewDelegateGtk::GetFor(web_contents())->
           expanded_container();
   gtk_container_add(GTK_CONTAINER(expanded_container), sad_tab_->widget());
   gtk_widget_show(sad_tab_->widget());
 #else
 #error Unknown platform
 #endif
 }