Also improve suppression of Math.pow precision.

BUG=chromium:679957
NOTRY=true
TBR=mstarzinger@chromium.org,jarin@chromium.org

Change-Id: I43d0cd6f6f6d0867be9f2337990114c07c716df5
Reviewed-on: https://chromium-review.googlesource.com/438327Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#42966}