Make using WebContentsUserData simpler.

chrome/browser/ui/pdf/pdf_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_PDF_PDF_TAB_HELPER_H_
 #define CHROME_BROWSER_UI_PDF_PDF_TAB_HELPER_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "chrome/browser/common/web_contents_user_data.h"
 #include "content/public/browser/web_contents_observer.h"
 
 class OpenPDFInReaderPromptDelegate;
 
 namespace content {
 class WebContents;
 }
 
 // Per-tab class to handle PDF messages.
 class PDFTabHelper : public content::WebContentsObserver,
                      public WebContentsUserData<PDFTabHelper>  {
  public:
-  static int kUserDataKey;
 
   explicit PDFTabHelper(content::WebContents* web_contents);
   virtual ~PDFTabHelper();
 
   OpenPDFInReaderPromptDelegate* open_in_reader_prompt() const {
     return open_in_reader_prompt_.get();
   }
 
   void ShowOpenInReaderPrompt(scoped_ptr<OpenPDFInReaderPromptDelegate> prompt);
 
@@ skipping 11 matching lines @@
   // Message handlers.
   void OnPDFHasUnsupportedFeature();
 
   // The model for the confirmation prompt to open a PDF in Adobe Reader.
   scoped_ptr<OpenPDFInReaderPromptDelegate> open_in_reader_prompt_;
 
   DISALLOW_COPY_AND_ASSIGN(PDFTabHelper);
 };
 
 #endif  // CHROME_BROWSER_UI_PDF_PDF_TAB_HELPER_H_