Having created composite ordering methods for the different kinds of animations
this patch adds a Comparator class so that they can be used to sort an
array of such animations.
This patch uses this Comparator object to sort the results returned by
Element.getAnimations. For this case, the order in which we create animations
and transitions happens to almost perfectly correspond with the composite
ordering defined so that no sorting is necessary.
One exception is that some -moz-* transitions may be created after transitions
that they should sort before when sorting by transition property. In this
case the sorting added in this patch should ensure they are returned in the
correct sequence.
Unfortunately, we can't easily test this since the test files we have are
intended to be cross-browser (where -moz-* properties won't be supported).
Once we implement AnimationTimeline.getAnimations (bug 1150810) we'll have
a better opportunity to test this sorting. For now, the added tests in this
patch just serve as a regression test that the sorting hasn't upset the
already correct order (and an interop test in future once we move them to
web-platform-tests).
