Switch Extensions::TabHelper to use WebContents, WebContentsUserData.

chrome/browser/sync/glue/session_change_processor.cc

Index: chrome/browser/sync/glue/session_change_processor.cc
diff --git a/chrome/browser/sync/glue/session_change_processor.cc b/chrome/browser/sync/glue/session_change_processor.cc
index 815220eba66d9720c0e35f3c7aff1e26006cb55a..2b98f6806c0322a85887a61ff426bac9d9e7df3a 100644
--- a/chrome/browser/sync/glue/session_change_processor.cc
+++ b/chrome/browser/sync/glue/session_change_processor.cc
@@ -181,14 +181,14 @@ void SessionChangeProcessor::Observe(
     case chrome::NOTIFICATION_TAB_CONTENTS_APPLICATION_EXTENSION_CHANGED: {
       extensions::TabHelper* extension_tab_helper =
           content::Source<extensions::TabHelper>(source).ptr();
-      if (!extension_tab_helper ||
-          extension_tab_helper->web_contents()->GetBrowserContext() !=
+      if (extension_tab_helper->web_contents()->GetBrowserContext() !=
               profile_) {
         return;
       }
       if (extension_tab_helper->extension_app()) {
-        modified_tabs.push_back(extension_tab_helper->tab_contents()->
-            synced_tab_delegate());
+        TabContents* tab_contents =
+            TabContents::FromWebContents(extension_tab_helper->web_contents());
+        modified_tabs.push_back(tab_contents->synced_tab_delegate());
       }
       DVLOG(1) << "Received TAB_CONTENTS_APPLICATION_EXTENSION_CHANGED "
                << "for profile " << profile_;