Switch Extensions::TabHelper to use WebContents, WebContentsUserData.

chrome/browser/ui/sync/tab_contents_synced_tab_delegate.cc

Index: chrome/browser/ui/sync/tab_contents_synced_tab_delegate.cc
diff --git a/chrome/browser/ui/sync/tab_contents_synced_tab_delegate.cc b/chrome/browser/ui/sync/tab_contents_synced_tab_delegate.cc
index a32ea503f43a940a53533735610d0137586fce77..4cab6ca53105ca2b2e28f517c23432404592474a 100644
--- a/chrome/browser/ui/sync/tab_contents_synced_tab_delegate.cc
+++ b/chrome/browser/ui/sync/tab_contents_synced_tab_delegate.cc
@@ -39,14 +39,15 @@ Profile* TabContentsSyncedTabDelegate::profile() const {
 }
 
 bool TabContentsSyncedTabDelegate::HasExtensionAppId() const {
-  return (tab_contents_->extension_tab_helper() &&
-      tab_contents_->extension_tab_helper()->extension_app());
+  return !!(extensions::TabHelper::FromWebContents(
+      tab_contents_->web_contents())->extension_app());
 }
 
 const std::string& TabContentsSyncedTabDelegate::GetExtensionAppId()
     const {
   DCHECK(HasExtensionAppId());
-  return tab_contents_->extension_tab_helper()->extension_app()->id();
+  return extensions::TabHelper::FromWebContents(tab_contents_->web_contents())->
+      extension_app()->id();
 }
 
 int TabContentsSyncedTabDelegate::GetCurrentEntryIndex() const {