Implement the ability to layout test Web Worker-based Notifications.

content/shell/renderer/layout_test/webkit_test_runner.h

Index: content/shell/renderer/layout_test/webkit_test_runner.h
diff --git a/content/shell/renderer/layout_test/webkit_test_runner.h b/content/shell/renderer/layout_test/webkit_test_runner.h
index 4bba3db561dc20b51c2e2caebdd409bac715a006..96f189bfa3344bd4779248002c46482f45d4a283 100644
--- a/content/shell/renderer/layout_test/webkit_test_runner.h
+++ b/content/shell/renderer/layout_test/webkit_test_runner.h
@@ -93,6 +93,7 @@ class WebKitTestRunner : public RenderViewObserver,
   void GrantWebNotificationPermission(const GURL& origin,
                                       bool permission_granted) override;
   void ClearWebNotificationPermissions() override;
+  void SimulateWebNotificationClick(const std::string& title) override;
   void SetDeviceScaleFactor(float factor) override;
   void SetDeviceColorProfile(const std::string& name) override;
   void SetFocus(WebTestProxyBase* proxy, bool focus) override;