The Atomics object is a normal object, just like Math, JSON, etc., so
we should be able to set it up in the same way those are set up
since cff5470a.

Change-Id: I46a9ba990707c0659f1a62f628b2c69204e536f8
Reviewed-on: https://chromium-review.googlesource.com/537076Reviewed-by: Ben Smith <binji@chromium.org>
Commit-Queue: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45964}