PSA: You can now view screenshots of failing reftests on wpt.fyi

Tl;dr. Go to this example
<https://wpt.fyi/results/css/css-position/position-relative-table-tbody-left-absolute-child.html?run_id=5668853719760896&run_id=5640982771007488&run_id=5907019957534720&run_id=6231803673182208>
and click "COMPARE".

Have you ever wondered why a WPT reftest
<https://web-platform-tests.org/writing-tests/reftests.html> failed? Did
you wish wpt.fyi could also show you the screenshots as the result viewers
in Blink/Gecko CI? Wait no more. Screenshots are now available on wpt.fyi
for reftest failures on all browsers and platforms! (Chrome & Firefox on
Linux, Edge on Windows, Safari on macOS)


   1. Navigate to any reftest with failure(s) on wpt.fyi (example
   <https://wpt.fyi/results/css/css-position/position-relative-table-tbody-left-absolute-child.html?run_id=5668853719760896&run_id=5640982771007488&run_id=5907019957534720&run_id=6231803673182208>
   ).
   2. Click on the "COMPARE" button next to any "FAIL".
   (If you don't see the button, you might need to force-reload the page.)
   3. In the newly introduced reftest analyzer, you can hover over the
   image to zoom into pixels and see the RGB values; you can also toggle the
   "difference" filter and switch between the test (before) and reference
   (after) screenshots.
   The UI is still in early stage (many thanks to Luke Bjerring!). Please
   feel empowered to make use of the "file an issue" link.


There's a lot more going on behind the scenes in order to produce the
screenshots on runners and store them on wpt.fyi. If you're interested, you
can find more details in the design doc
<https://docs.google.com/document/d/1IhZa4mrjK1msUMhtamKwKJ_HhXD-nqh_4-BcPWM6soQ/>
.

If you have any other questions, feel free to reach out to
ecosystem-infra@chromium.org.

Regards,
Robert from the Ecosystem Infra team