Rewrite svg/animations/getCurrentTime-pause-unpause.html to avoid flakes

The test in it's current form imposed too strict requirements on the
time that had passed. We cannot guarantee a maximum elapsed time, only a
minimum (and barely that...) Rewrite the test to not impose any
restriction on the maximum elapsed time. Also convert it to use
testharness while at it. Also rewrite/convert the sibling test with
setCurrentTime.

Bug: 824930
Change-Id: I79882b0189e44790e3096c8346c2a0bf47276dd8
Reviewed-on: https://chromium-review.googlesource.com/981145
Reviewed-by: Stephen Chenney <schenney@chromium.org>
Commit-Queue: Fredrik Söderquist <fs@opera.com>
Cr-Commit-Position: refs/heads/master@{#546190}
4 files changed