Register a Service Worker when an extension is enabled.

chrome/browser/extensions/extension_host.h

Index: chrome/browser/extensions/extension_host.h
diff --git a/chrome/browser/extensions/extension_host.h b/chrome/browser/extensions/extension_host.h
index ca25efbcf35c8934cd4e07405164b7d69afc032d..45576546b0cfd8db0e38ebc9acf6765b571d957e 100644
--- a/chrome/browser/extensions/extension_host.h
+++ b/chrome/browser/extensions/extension_host.h
@@ -70,7 +70,7 @@ 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);
 };