Make using WebContentsUserData simpler.

chrome/browser/extensions/api/web_navigation/web_navigation_api.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.
 
 // Defines the Chrome Extensions WebNavigation API functions for observing and
 // intercepting navigation events, as specified in the extension JSON API.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_API_WEB_NAVIGATION_WEB_NAVIGATION_API_H_
 #define CHROME_BROWSER_EXTENSIONS_API_WEB_NAVIGATION_WEB_NAVIGATION_API_H_
 
@@ skipping 79 matching lines @@
   virtual void DidOpenRequestedURL(content::WebContents* new_contents,
                                    const GURL& url,
                                    const content::Referrer& referrer,
                                    WindowOpenDisposition disposition,
                                    content::PageTransition transition,
                                    int64 source_frame_num) OVERRIDE;
   virtual void WebContentsDestroyed(content::WebContents* tab) OVERRIDE;
 
  private:
   explicit WebNavigationTabObserver(content::WebContents* web_contents);
-  static int kUserDataKey;
   friend class WebContentsUserData<WebNavigationTabObserver>;
 
   // True if the transition and target url correspond to a reference fragment
   // navigation.
   bool IsReferenceFragmentNavigation(FrameNavigationState::FrameID frame_id,
                                      const GURL& url);
 
   // Creates and sends onErrorOccurred events for all on-going navigations. If
   // |render_view_host| is non-NULL, only generates events for frames in this
   // render view host. If |id_to_skip| is given, no events are sent for that
@@ skipping 100 matching lines @@
 // API function that returns the states of all frames in a given tab.
 class GetAllFramesFunction : public SyncExtensionFunction {
   virtual ~GetAllFramesFunction() {}
   virtual bool RunImpl() OVERRIDE;
   DECLARE_EXTENSION_FUNCTION_NAME("webNavigation.getAllFrames")
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_WEB_NAVIGATION_WEB_NAVIGATION_API_H_