window.onresize is not intercepted by zones

Repro snippet:

```js
window.onresize = () => console.trace('stack from within onresize handler');
```

Zone check from within the onresize handler:
```
> window.Zone.current
Zone {_properties: Object, _parent: null, _name: "<root>", _zoneDelegate: ZoneDelegate}
```

We came across this via angular/angular#16143