Add layout tests for ServiceWorker's notificationclose event.

content/shell/browser/layout_test/layout_test_message_filter.h

Index: content/shell/browser/layout_test/layout_test_message_filter.h
diff --git a/content/shell/browser/layout_test/layout_test_message_filter.h b/content/shell/browser/layout_test/layout_test_message_filter.h
index 1a0909cdd583f9f943fa925642cff5e71df23ded..8c4bb5d8bd22aaec6f36e7b6a247c3f9a4938bfa 100644
--- a/content/shell/browser/layout_test/layout_test_message_filter.h
+++ b/content/shell/browser/layout_test/layout_test_message_filter.h
@@ -56,6 +56,7 @@ class LayoutTestMessageFilter : public BrowserMessageFilter {
   void OnClearWebNotificationPermissions();
   void OnSimulateWebNotificationClick(const std::string& title,
                                       int action_index);
+  void OnSimulateWebNotificationClose(const std::string& title, bool by_user);
   void OnSetPushMessagingPermission(const GURL& origin, bool allowed);
   void OnClearPushMessagingPermissions();
   void OnAcceptAllCookies(bool accept);