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When catching up the animation, if the StartAnimation call for
advancing the next frame was delayed, if n is the desired current frame,
we advance uptill frame n-1 and a post a task to further advance to
frame n. This task also calls StartAnimation to schedule a task for
the next frame of the animation. In this call, kDoNotCatchUp is used to
avoid going through a catch up loop and schedule this task immediately
if necessary.

Clean up the logic to advance to frame n during catch up and schedule
the next task synchronously. And add a test.

R=chrishtr@chromium.org

Change-Id: I5fdb1d978001b0bf5f04cdaf4dada110db065801
Reviewed-on: https://chromium-review.googlesource.com/674056
Commit-Queue: Khushal <khushalsagar@chromium.org>
Reviewed-by: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#504249}