Make using WebContentsUserData simpler.

chrome/browser/ui/zoom/zoom_controller.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_ZOOM_ZOOM_CONTROLLER_H_
 #define CHROME_BROWSER_UI_ZOOM_ZOOM_CONTROLLER_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "chrome/browser/api/prefs/pref_member.h"
@@ skipping 20 matching lines @@
   // Convenience method to quickly check if the tab's at default zoom.
   bool IsAtDefaultZoom() const;
 
   // Returns which image should be loaded for the current zoom level.
   int GetResourceForZoomLevel() const;
 
   void set_observer(ZoomObserver* observer) { observer_ = observer; }
 
  private:
   explicit ZoomController(content::WebContents* web_contents);
-  static int kUserDataKey;
   friend class WebContentsUserData<ZoomController>;
 
   // content::WebContentsObserver overrides:
   virtual void DidNavigateMainFrame(
       const content::LoadCommittedDetails& details,
       const content::FrameNavigateParams& params) OVERRIDE;
 
   // content::NotificationObserver overrides:
   virtual void Observe(int type,
                        const content::NotificationSource& source,
@@ skipping 13 matching lines @@
   // Used to access the default zoom level preference.
   DoublePrefMember default_zoom_level_;
 
   // Observer receiving notifications on state changes.
   ZoomObserver* observer_;
 
   DISALLOW_COPY_AND_ASSIGN(ZoomController);
 };
 
 #endif  // CHROME_BROWSER_UI_ZOOM_ZOOM_CONTROLLER_H_