[css-fonts] Test for rem/em dimensions based on :root font-size

6 years ago I filed a bug in
https://bugs.chromium.org/p/chromium/issues/detail?id=308862 and lately it
has been picked up by both Chromium developers and web developers.

The short description is that, using percentage value in :root{ font-size
}  below a certain threshold does not translate to correct rem/em values in
blink and webkit. It does work as advertised on w3, in Edge and Firefox. <
https://www.w3.org/TR/css-values-3/#rem>

I have look at the test cases in <
https://github.com/web-platform-tests/wpt/tree/master/css/css-values> and
searched in issues <
https://github.com/web-platform-tests/wpt/issues?utf8=%E2%9C%93&q=is%3Aissue+REM+font-size>
but have not found anything that suggest that there exist a test for this
issue.

Myself and others have provided several test cases in the chromium issue <
https://bugs.chromium.org/p/chromium/issues/detail?id=308862> and I am
wondering if it is feasible to translate a simple one of them into a test
in the web-platform-tests Project.

I don't have any experience writing these kind of tests and would need help
to get started. I imagine that it could be a reftest <
https://web-platform-tests.org/writing-tests/reftests.html> which could be
run automatically.

Is there interest in this kind of test, is it the right place for such a
test and how do I get started?