Create thread-safe RendererExtensionRegistry from ExtensionSet

extensions/renderer/script_injection_manager.h

Index: extensions/renderer/script_injection_manager.h
diff --git a/extensions/renderer/script_injection_manager.h b/extensions/renderer/script_injection_manager.h
index 88f552071f323b15bf13e579457d5faf9b79d394..5eda418bd1a5057b525672a169b89174cd3502e3 100644
--- a/extensions/renderer/script_injection_manager.h
+++ b/extensions/renderer/script_injection_manager.h
@@ -25,7 +25,6 @@ class RenderFrame;
 
 namespace extensions {
 class Extension;
-class ExtensionSet;
 
 // The ScriptInjectionManager manages extensions injecting scripts into frames
 // via both content/user scripts and tabs.executeScript(). It is responsible for
@@ -33,8 +32,8 @@ class ExtensionSet;
 // load point, and injecting them when ready.
 class ScriptInjectionManager : public UserScriptSetManager::Observer {
  public:
-  ScriptInjectionManager(const ExtensionSet* extensions,
-                         UserScriptSetManager* user_script_set_manager);
+  explicit ScriptInjectionManager(
+      UserScriptSetManager* user_script_set_manager);
   virtual ~ScriptInjectionManager();
 
   // Notifies that a new render view has been created.
@@ -92,9 +91,6 @@ class ScriptInjectionManager : public UserScriptSetManager::Observer {
   // Handle the GrantInjectionPermission extension message.
   void HandlePermitScriptInjection(int64 request_id);
 
-  // Extensions metadata, owned by Dispatcher (which owns this object).
-  const ExtensionSet* extensions_;
-
   // The map of active web frames to their corresponding statuses. The
   // RunLocation of the frame corresponds to the last location that has ran.
   FrameStatusMap frame_statuses_;