Fix standalone compilation on Mac
Fix standalone compilation on Mac

The std::pair constructor isn't constexpr there.

BUG=

Change-Id: I7711185c6c991fd5793cc6c785e9905710660cd9
Reviewed-on: https://chromium-review.googlesource.com/723849
Reviewed-by: Jamie Madill <7e492b4f1c8458024932de3ba475cbf015424c30@chromium.org>
Commit-Queue: Corentin Wallez <470c533e86f4f848c98c7e11fffc2d043494a401@chromium.org>

ppy/angle,ppy/angle,ppy/angle,ppy/angle