This will have two benefits:
1) Align test setup with shipping Firefox - We don't allow content
privilege XUL in shipping versions of Firefox, so having the tests be
chrome would be more realistic to our use case.
2) Support the XUL to XHTML migration. These files will soon become XHTML
files, but will still need to load XUL elements, so they'll need to be
marked as chrome privileged to continue working.
One test (404149-1.xul) is now disabled, since it fails when loaded as
chrome. Bug 1557383 was filed to address this.
Differential Revision: https://phabricator.services.mozilla.com/D33986
--HG--
extra : moz-landing-system : lando
