Don't know if a regression range is still required since I see that Paul already has a patch but I did found a regression between the nightly builds from 2020-01-10: https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=feb7d997f96164b028c9cf57a74878095cdad0d3&tochange=12bf9dc0978e049c367ba4c22052569c3acb1e50 I tried to dig deeper with mozregression but I got mixed results every time so it's not reliable. Hope this helps.
Bug 1636496 Comment 8 Edit History
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Don't know if a regression range is still required since I see that Paul already has a patch but I did found a regression between the nightly builds from 2020-01-10: https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=feb7d997f96164b028c9cf57a74878095cdad0d3&tochange=12bf9dc0978e049c367ba4c22052569c3acb1e50 (not sure of the potential regressor there) I tried to dig deeper with mozregression but I got mixed results every time so it's not reliable. Hope this helps.