If reftest-no-flush is not specified, reftest harness flushes layout in a
callback of setTimeout() that happens after paint process happened in the next
refresh driver's tick. Thus, the paint process triggered by the layout flush
causes no invalidation changes, so reftest harness ends up waiting for the
animation end until the animation finishes.
MozReview-Commit-ID: GXvmyXh0kfV
--HG--
extra : rebase_source : 091a91122b7337ff05032bd64fa2597e59bed3a4