The detailed story was in https://bugs.webkit.org/show_bug.cgi?id=50386. Echo Alexey's suggestion, add a layout test to avoid future regressions. Creating this bug is about to track the patch.
Created attachment 75590 [details] patch
Comment on attachment 75590 [details] patch It's confusing that the result is written out at the end of each stage - it's only the second write that matters.
Created attachment 75600 [details] patch V2 (In reply to comment #2) > (From update of attachment 75590 [details]) > It's confusing that the result is written out at the end of each stage - it's only the second write that matters. You are right, I think the test should stop once it encounters a failure. Here is the new patch, please take a look:)
The commit-queue encountered the following flaky tests while processing attachment 75600 [details]: fast/preloader/script.html animations/combo-transform-translate+scale.html Please file bugs against the tests. These tests were authored by abarth@webkit.org, cmarrin@apple.com, darin@apple.com, ojan@chromium.org, and pol@apple.com. The commit-queue is continuing to process your patch.
Comment on attachment 75600 [details] patch V2 Clearing flags on attachment: 75600 Committed r73327: <http://trac.webkit.org/changeset/73327>
All reviewed patches have been landed. Closing bug.