Switch WebContentsUserData to be a friended base.

BUG=107201
TEST=no visible change


Review URL: https://chromiumcodereview.appspot.com/10933105

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@156988 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/chrome/browser/extensions/tab_helper.h b/chrome/browser/extensions/tab_helper.h
index cad235e..05a2665 100644
--- a/chrome/browser/extensions/tab_helper.h
+++ b/chrome/browser/extensions/tab_helper.h
@@ -51,9 +51,7 @@
     UPDATE_SHORTCUT   // Update icon for app shortcut.
   };
 
-  explicit TabHelper(content::WebContents* web_contents);
   virtual ~TabHelper();
-  static int kUserDataKey;
 
   void CreateApplicationShortcuts();
   bool CanCreateApplicationShortcuts() const;
@@ -115,6 +113,10 @@
   void SetAppIcon(const SkBitmap& app_icon);
 
  private:
+  explicit TabHelper(content::WebContents* web_contents);
+  static int kUserDataKey;
+  friend class WebContentsUserData<TabHelper>;
+
   // content::WebContentsObserver overrides.
   virtual void RenderViewCreated(
       content::RenderViewHost* render_view_host) OVERRIDE;