Bug 1352523, add more hacks to browser_parsable_css.js to make it not fail randomly, r=poirot

--HG--
extra : rebase_source : c3008d8e8fbb13f64986e5892f654ead7a74be32

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

@@ -53,6 +53,10 @@ let whitelist = [
    intermittent: true,
    errorMessage: /Property contained reference to invalid variable.*color/i,
    isFromDevTools: true},
+  {sourceName: /webide\/skin\/logs\.css$/i,
+   intermittent: true,
+   errorMessage: /Property contained reference to invalid variable.*background/i,
+   isFromDevTools: true},
   {sourceName: /devtools\/skin\/animationinspector\.css$/i,
    intermittent: true,
    errorMessage: /Property contained reference to invalid variable.*color/i,