Implement window.requestPostAnimationFrame

This can only be called from within a requestAnimationFrame callback.
It registers a callback that will run synchronously at the end of a
lifecycle update, with no possibility of any other javascript running
before it.

Bug: 956293
Change-Id: I9e42ef043588134ed9ded638e1f8474eedbf800b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1423738
Reviewed-by: Klaus Weidner <klausw@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Commit-Queue: Stefan Zager <szager@chromium.org>
Cr-Commit-Position: refs/heads/master@{#654321}
19 files changed