Don't close background pages if there is a pending response (callback).

chrome/renderer/extensions/extension_dispatcher.h

Index: chrome/renderer/extensions/extension_dispatcher.h
diff --git a/chrome/renderer/extensions/extension_dispatcher.h b/chrome/renderer/extensions/extension_dispatcher.h
index d6822ec154c9f49a025e82cc7132bbdec602b538..661e2bb669695ba5236bd742e1cec04833487b4d 100644
--- a/chrome/renderer/extensions/extension_dispatcher.h
+++ b/chrome/renderer/extensions/extension_dispatcher.h
@@ -81,6 +81,10 @@ class ExtensionDispatcher : public content::RenderProcessObserver {
     return webrequest_other_;
   }
 
+  // If the extension is in fact idle, tell the browser process to close
+  // the background page.
+  void OnExtensionIdle(const std::string& extension_id);
+
  private:
   friend class RenderViewTest;