Switch Extensions::TabHelper to use WebContents, WebContentsUserData.

chrome/browser/ui/tab_contents/tab_contents.h

Index: chrome/browser/ui/tab_contents/tab_contents.h
diff --git a/chrome/browser/ui/tab_contents/tab_contents.h b/chrome/browser/ui/tab_contents/tab_contents.h
index 09b9f25202b273397bd7366bdaeb49b4f3504d3e..b66e0aa5c6837e6814acfc9986881d2581f8dfed 100644
--- a/chrome/browser/ui/tab_contents/tab_contents.h
+++ b/chrome/browser/ui/tab_contents/tab_contents.h
@@ -104,7 +104,6 @@ class WebUILoginView;
 }
 
 namespace extensions {
-class TabHelper;
 class WebAuthFlow;
 class WebNavigationTabObserver;
 }
@@ -236,14 +235,6 @@ class TabContents : public content::WebContentsObserver {
 
   CoreTabHelper* core_tab_helper() { return core_tab_helper_.get(); }
 
-  extensions::TabHelper* extension_tab_helper() {
-    return extension_tab_helper_.get();
-  }
-
-  const extensions::TabHelper* extension_tab_helper() const {
-    return extension_tab_helper_.get();
-  }
-
   FaviconTabHelper* favicon_tab_helper() { return favicon_tab_helper_.get(); }
   FindTabHelper* find_tab_helper() { return find_tab_helper_.get(); }
   HistoryTabHelper* history_tab_helper() { return history_tab_helper_.get(); }
@@ -344,7 +335,6 @@ class TabContents : public content::WebContentsObserver {
 #endif
   scoped_ptr<ConstrainedWindowTabHelper> constrained_window_tab_helper_;
   scoped_ptr<CoreTabHelper> core_tab_helper_;
-  scoped_ptr<extensions::TabHelper> extension_tab_helper_;
   scoped_ptr<FaviconTabHelper> favicon_tab_helper_;
   scoped_ptr<FindTabHelper> find_tab_helper_;
   scoped_ptr<HistoryTabHelper> history_tab_helper_;