The best practice is to expose a non-constexpr query function and
hide the constexpr table in a cpp, so it won't be included verbatim
in multiple other source files.

BUG=angleproject:1389

Change-Id: Ic4e19d14c832643be1552c5a14e441826c41970f
Reviewed-on: https://chromium-review.googlesource.com/404478Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>