tests involving downloads with parent-controlled navigation

[Andrew McCreight]

I've enabled parent-controlled navigation in bug 1746524.

One issue is that tests involving downloads now have to be done in a slightly different way.

You now have to do this:

await BrowserTestUtils.openNewForegroundTab({
  gBrowser,
  opening: downloadUrl,
  waitForLoad: false,
  waitForStateStop: true,
});

instead of this:

await BrowserTestUtils.openNewForegroundTab(
  gBrowser,
  downloadUrl
);

See bug 1776080 for an example. Sorry for the inconvenience.

Also please let me know if you notice any new page navigation related weirdness.

Thanks,

Andrew