Chat drawer was using the `DiscourseURL` hook `afterRouteComplete`. This hook suffer from a very poor implementation which makes it very unreliable:
```javascript
if (typeof opts.afterRouteComplete === "function") {
schedule("afterRender", opts.afterRouteComplete);
}
```
This commit attempts to return the promise from `handleURL` to directly use it and have a very reliable after transition hook.
f0d82de5d9