When ANGLE is used with Chromium, having two copies of safe numerics
code in namespace base causes ODR violations.

BUG=449754

Change-Id: I686049e7d8926373d00dd17ec8142fa3c508b9c5
Reviewed-on: https://chromium-review.googlesource.com/513434Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>