Layout test inspector/heap/getPreview.html has been a flaky timeout for the GTK port since r201001-r201016. r201016 is actually the first good commit after a long string of consistent timeouts. Updating expectations accordingly.
Now it is consistently failing, after r228546. This is caused by https://bugs.webkit.org/show_bug.cgi?id=180607 and it's affecting Mac as well. I am updating the test expectation and because the flakiness seems gone I will close this bug and update the bug reference in the TestExpectations file as well.