Kinuko is still trying to track down where this is happening, but it seems to be triggerable by running fast/filesystem/workers/file-from-file-entry-sync.html. See Chromium try job failure: http://build.chromium.org/p/tryserver.chromium/builders/mac/builds/15549/steps/ui_tests/logs/WorkerFileSystemFileFromFileEntrySyncTest So far, only triggered on Mac, but no reason to think this is platform-specific.
This doesn't seem to be specific to the file-from-file-entry-sync test. Here's the same failure in another test: http://build.chromium.org/p/tryserver.chromium/builders/mac/builds/16102/steps/ui_tests/logs/FileWriterSyncTruncateExtend
Created attachment 85118 [details] Patch
Comment on attachment 85118 [details] Patch View in context: https://bugs.webkit.org/attachment.cgi?id=85118&action=review > Source/WebKit/chromium/ChangeLog:11 > + (this could happen before or after the runTaskOnWorkerThread) do s/do/does/
Committed r80617: <http://trac.webkit.org/changeset/80617>
http://trac.webkit.org/changeset/80617 might have broken GTK Linux 32-bit Debug