reftest-analyzer view of the piece of the log that I just attached: https://hg.mozilla.org/mozilla-central/raw-file/tip/layout/tools/reftest/reftest-analyzer.xhtml#logurl=https://bug1821482.bmoattachments.org/attachment.cgi?id=9322228 No text involved in these tests (so not a text antialiasing thing -- though when you're looking at testcases with text, that's a good default assumption). The mismatching pixels are random pixels at the edges of shapes, with a barely mismatching color channel. Looks like bit-flips from bad RAM.
Bug 1821482 Comment 4 Edit History
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reftest-analyzer view of the piece of the log that I just attached: [EDIT: looks like there's a CSP that prevents reftest-analyzer from automagically working with bugzilla atachments, but you can copypaste the attachment's contents into https://hg.mozilla.org/mozilla-central/raw-file/tip/layout/tools/reftest/reftest-analyzer.xhtml and hit "process pasted log"] No text involved in these tests (so not a text antialiasing thing -- though when you're looking at testcases with text, that's a good default assumption). The mismatching pixels are random pixels at the edges of shapes, with a barely mismatching color channel. Looks like bit-flips from bad RAM.