Bug 1359302 - Update the browser_parsable_css.js whitelist to expect that ua.css and html.css might be loaded from gre-resources, r=Gijs

MozReview-Commit-ID: HJGL8CUylNi

--HG--
extra : rebase_source : 7ae028a6d9423b45ed68ea76be113bf3731b1678

browser/base/content/test/static/browser_parsable_css.js

@@ -65,7 +65,7 @@ let whitelist = [
 
 if (!Services.prefs.getBoolPref("full-screen-api.unprefix.enabled")) {
   whitelist.push({
-    sourceName: /res\/(ua|html)\.css$/i,
+    sourceName: /(?:res|gre-resources)\/(ua|html)\.css$/i,
     errorMessage: /Unknown pseudo-class .*\bfullscreen\b/i,
     isFromDevTools: false
   });