Layout test fast/css/will-change/will-change-creates-stacking-context.html has been failing since it was added in r188514 ("Have will-change create stacking context when necessary"). It is failing in exactly the same way that fast/css/will-change/will-change-creates-stacking-context-inline.html is failing in bug #163977, but this test has been failing for longer. Updating expectations accordingly.
Test is passing since r264968.