Create thread-safe RendererExtensionRegistry from ExtensionSet

extensions/renderer/user_script_set.h

Index: extensions/renderer/user_script_set.h
diff --git a/extensions/renderer/user_script_set.h b/extensions/renderer/user_script_set.h
index a39a543bc3789fb30f54599f2129596055c50def..231722e8d1137920e11d5c5b96063af268a2e646 100644
--- a/extensions/renderer/user_script_set.h
+++ b/extensions/renderer/user_script_set.h
@@ -24,7 +24,6 @@ class RenderFrame;
 }
 
 namespace extensions {
-class ExtensionSet;
 class ScriptInjection;
 
 // The UserScriptSet is a collection of UserScripts which knows how to update
@@ -39,7 +38,7 @@ class UserScriptSet {
         const std::vector<UserScript*>& scripts) = 0;
   };
 
-  explicit UserScriptSet(const ExtensionSet* extensions);
+  UserScriptSet();
   ~UserScriptSet();
 
   // Adds or removes observers.
@@ -87,9 +86,6 @@ class UserScriptSet {
   // Shared memory containing raw script data.
   scoped_ptr<base::SharedMemory> shared_memory_;
 
-  // The set of all known extensions. Owned by the Dispatcher.
-  const ExtensionSet* extensions_;
-
   // The UserScripts this injector manages.
   ScopedVector<UserScript> scripts_;