fix #536, add notification api patch

[JiaLiPassion]

Patch notification API,
because EventTarget has been patched already, so

  notification.addEventListener

is already patched.

This PR just patched onclick, onerror property.

  Zone.current.fork({name: 'test'}).run(function() {
      n.onclick = function() {
          expect(Zone.current.name).toEqual('test');
      }
 });