Make using WebContentsUserData simpler.

chrome/browser/ui/tab_contents/core_tab_helper.h

 // 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.
 
 #ifndef CHROME_BROWSER_UI_TAB_CONTENTS_CORE_TAB_HELPER_H_
 #define CHROME_BROWSER_UI_TAB_CONTENTS_CORE_TAB_HELPER_H_
 
 #include "chrome/browser/common/web_contents_user_data.h"
 #include "content/public/browser/web_contents_observer.h"
 
 class CoreTabHelperDelegate;
 
 // Per-tab class to handle functionality that is core to the operation of tabs.
 class CoreTabHelper : public content::WebContentsObserver,
                       public WebContentsUserData<CoreTabHelper> {
  public:
   virtual ~CoreTabHelper();
 
   CoreTabHelperDelegate* delegate() const { return delegate_; }
   void set_delegate(CoreTabHelperDelegate* d) { delegate_ = d; }
 
   // Initial title assigned to NavigationEntries from Navigate.
   static string16 GetDefaultTitle();
 
   // Returns a human-readable description the tab's loading state.
   string16 GetStatusText() const;
 
  private:
   explicit CoreTabHelper(content::WebContents* web_contents);
-  static int kUserDataKey;
   friend class WebContentsUserData<CoreTabHelper>;
 
   // content::WebContentsObserver overrides:
   virtual void WasShown() OVERRIDE;
 
   // Delegate for notifying our owner about stuff. Not owned by us.
   CoreTabHelperDelegate* delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(CoreTabHelper);
 };
 
 #endif  // CHROME_BROWSER_UI_TAB_CONTENTS_CORE_TAB_HELPER_H_