Switch ZoomTabHelper to use WebContentsUserData.

chrome/browser/ui/browser.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_BROWSER_H_
 #define CHROME_BROWSER_UI_BROWSER_H_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 654 matching lines @@
 
   // Overridden from BlockedContentTabHelperDelegate:
   virtual content::WebContents* GetConstrainingWebContents(
       content::WebContents* source) OVERRIDE;
 
   // Overridden from BookmarkTabHelperDelegate:
   virtual void URLStarredChanged(content::WebContents* web_contents,
                                  bool starred) OVERRIDE;
 
   // Overridden from ZoomObserver:
-  virtual void OnZoomChanged(TabContents* source,
+  virtual void OnZoomChanged(content::WebContents* source,
                              bool can_show_bubble) OVERRIDE;
 
   // Overridden from SelectFileDialog::Listener:
   virtual void FileSelected(const FilePath& path,
                             int index,
                             void* params) OVERRIDE;
   virtual void FileSelectedWithExtraInfo(
       const ui::SelectedFileInfo& file_info,
       int index,
       void* params) OVERRIDE;
@@ skipping 249 matching lines @@
   bool window_has_shown_;
 
   // Currently open color chooser. Non-NULL after OpenColorChooser is called and
   // before DidEndColorChooser is called.
   scoped_ptr<content::ColorChooser> color_chooser_;
 
   DISALLOW_COPY_AND_ASSIGN(Browser);
 };
 
 #endif  // CHROME_BROWSER_UI_BROWSER_H_