Register a Service Worker when an extension is enabled.

extensions/browser/extension_host.h

Index: extensions/browser/extension_host.h
diff --git a/extensions/browser/extension_host.h b/extensions/browser/extension_host.h
index e10a98ffc723c95ef726948a0b9f699e1fc9cc10..a567b667caddb903c28dc6fff8ccf07c412b267a 100644
--- a/extensions/browser/extension_host.h
+++ b/extensions/browser/extension_host.h
@@ -73,7 +73,7 @@ class ExtensionHost : public content::WebContentsDelegate,
   // Prepares to initializes our RenderViewHost by creating its RenderView and
   // navigating to this host's url. Uses host_view for the RenderViewHost's view
   // (can be NULL). This happens delayed to avoid locking the UI.
-  void CreateRenderViewSoon();
+  void CreateRenderViewSoon(const base::Closure& continuation);
 
   // content::WebContentsObserver
   virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE;
@@ -177,6 +177,9 @@ class ExtensionHost : public content::WebContentsDelegate,
   // Used to measure how long it's been since the host was created.
   base::ElapsedTimer since_created_;
 
+  // Called when the RenderView is created.
+  std::vector<base::Closure> when_render_view_created_;
+
   DISALLOW_COPY_AND_ASSIGN(ExtensionHost);
 };