According to mozregression bug 1255108 and bug 1255106 introduced this png display artefact as shown in the screenshot.
- Install brief from https://addons.mozilla.org/en-US/firefox/addon/brief/
- Go to any rss feed like https://planet.mozilla.org/
- In the page action bar (in awesome bar) click on the RSS feed to subscribe
- In browser action bar click on brief RSS icon
- In Brief click on "all items"
- Then switch to "View headlines" in brief (which is on the top right). Looks like a hamburger menu
There should be no graphic glitches
7. On the right the arrow png icon has an artefact recently.
I tried to create a minimal working example at https://codepen.io/nachtigall/full/zQQWYB but was no really able to get all the relevant html/css in it to reproduce it, but maybe it helps as a skeleton...
fwiw, I run this:
$ mozregression --bad=2019-06-05 --good=2017-05-20 --addon brief-2.6.0b2-fx.xpi --arg="https://planet.mozilla.org/"
86:48.16 INFO: Last good revision: ca4f3b736dd6cbe6e1b195a4800b009ea55bf91d
86:48.16 INFO: First bad revision: 44fa715640dd2a4d06014e6d5fdda63c52707188
86:48.16 INFO: Pushlog: