The check of negative elapsedDuration is basically no longer valid since
animation delay is not factored into start time any more. But still we have
somtimes met negative elapsedDuration sice we use a previous vsync time stamp
for async animations to make the animations more sync. This is not a problem
in most cases but makes two reftests intermitent failure because both of them
used steps(1, start), the steps(1, start) composed different results in the
before phase and in the active phase. To avoid this difference this patch
replace the steps(1, start) with steps(1, end).
Once we incorpolate playbackRate into GetCurrentOrPendingStartTime, we don't
need to call AnimationTimeToTimeStamp for deviding delay by playbackRate since
the time passed to AnimationTimeToTimeStamp does not contain delay any more.
MozReview-Commit-ID: IVE2IFfNgm0
These tests aim to confirm that part 5 does not cause any regressons.
Adding this bunch of reftests makes a slight change in the result of
layout/reftests/bugs/395107-2.html on Android, so fuzzy-if was also
added for the test.
MozReview-Commit-ID: BtZ1OGiilmQ
