Switch Extensions::TabHelper to use WebContents, WebContentsUserData.

chrome/browser/ui/extensions/application_launch.cc

Index: chrome/browser/ui/extensions/application_launch.cc
diff --git a/chrome/browser/ui/extensions/application_launch.cc b/chrome/browser/ui/extensions/application_launch.cc
index 9af96e0aca41b02e8d0e92515d563879b66f3261..0e1e4e9bff16fdbe8ffd77d8e77fde4f333448ee 100644
--- a/chrome/browser/ui/extensions/application_launch.cc
+++ b/chrome/browser/ui/extensions/application_launch.cc
@@ -282,14 +282,13 @@ WebContents* OpenAppShortcutWindow(Profile* profile,
   if (!tab)
     return NULL;
 
-  TabContents* tab_contents = TabContents::FromWebContents(tab);
   // Set UPDATE_SHORTCUT as the pending web app action. This action is picked
   // up in LoadingStateChanged to schedule a GetApplicationInfo. And when
   // the web app info is available, extensions::TabHelper notifies Browser via
   // OnDidGetApplicationInfo, which calls
   // web_app::UpdateShortcutForTabContents when it sees UPDATE_SHORTCUT as
   // pending web app action.
-  tab_contents->extension_tab_helper()->set_pending_web_app_action(
+  extensions::TabHelper::FromWebContents(tab)->set_pending_web_app_action(
       extensions::TabHelper::UPDATE_SHORTCUT);
 
   return tab;