Make using WebContentsUserData simpler.

chrome/browser/ui/metro_pin_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/metro_pin_tab_helper.h"
 
 #include "base/logging.h"
 #include "base/utf_string_conversions.h"
 #include "content/public/browser/web_contents.h"
 
 #if defined(OS_WIN)
 #include "base/win/metro.h"
 #endif
 
-int MetroPinTabHelper::kUserDataKey;
+DEFINE_WEB_CONTENTS_USER_DATA_KEY(MetroPinTabHelper)
 
 MetroPinTabHelper::MetroPinTabHelper(content::WebContents* web_contents)
     : content::WebContentsObserver(web_contents),
       is_pinned_(false) {}
 
 MetroPinTabHelper::~MetroPinTabHelper() {}
 
 void MetroPinTabHelper::TogglePinnedToStartScreen() {
 #if defined(OS_WIN)
   HMODULE metro_module = base::win::GetMetroModule();
@@ skipping 41 matching lines @@
       return;
     }
 
     GURL url = web_contents()->GetURL();
     is_pinned_ = metro_is_pinned_to_start_screen(UTF8ToUTF16(url.spec())) != 0;
     VLOG(1) << __FUNCTION__ << " with url " << UTF8ToUTF16(url.spec())
             << " result: " << is_pinned_;
   }
 #endif
 }