Check whether we need to switch any resource:// files to chrome://
Context: #40134 (comment 2711427).
In the 82 bug review I saw some tickets switching resources from resource:// to chrome:// URIs. According to https://phabricator.services.mozilla.com/D85023#2640166 the reason is https://bugzilla.mozilla.org/show_bug.cgi?id=1145314 (and the patch https://hg.mozilla.org/mozilla-central/rev/915aa6a1a0edaeb9d65bc87e7f2ef7c4693cabfc). This seems to be more restrictive about loading "UI resource URIs", so we should check whether we are affected. A quick look at our code shows only resource://onboarding/*, resource://torbutton-assets and resource://torbutton-abouttor as potentially affected by this. It's possible that the changes in torbutton#40012 (closed) were needed because of this.