Fixed https://bugs.webkit.org/show_bug.cgi?id=22870

    Fixed https://bugs.webkit.org/show_bug.cgi?id=22870

        I added calls beginAnimationUpdate() and endAnimationUpdate() calls
        to AnimationController. These are called by Document at the start
        and end of the recalcStyle cycle. Right now, I'm just using the
        beginAnimationUpdate() method to reset an animation time value.
        The first time the animation time is accessed after this reset I set
        it to the currentTime. So all animations in that cycle get the same
        start time.

        The test cases checked in test this, but in the case of the 'left'
        test it actually doesn't make any difference in most cases. This is
        because values are clamped to whole pixels, so the start times would
        have to be pretty far off for the test to fail using the old
        currentTime() model. Still, under really heavy load, it's possible for
        the test to fail without these changes.

        The 'transform' test is another story. It animates to the full resolution
        of a floating point number, so the test fails miserably without this
        fix.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@39667 268f45cc-cd09-0410-ab3c-d52691b4dbfc