Revert of Stop copying script contents for each RenderFrames.

extensions/renderer/user_script_injector.h

Index: extensions/renderer/user_script_injector.h
diff --git a/extensions/renderer/user_script_injector.h b/extensions/renderer/user_script_injector.h
index cb89271d91fa5b06e81588b9b9907551bb1461d6..91716559c3a7f27ba44b1afda3f7abf114fd2691 100644
--- a/extensions/renderer/user_script_injector.h
+++ b/extensions/renderer/user_script_injector.h
@@ -63,11 +63,6 @@
   // this object.
   const UserScript* script_;
 
-  // The UserScriptSet that eventually owns the UserScript this
-  // UserScriptInjector points to.
-  // Outlives |this|.
-  UserScriptSet* const user_script_set_;
-
   // The id of the associated user script. We cache this because when we update
   // the |script_| associated with this injection, the old referance may be
   // deleted.