We were including the cpp in multiple targets, which was causing a
multiply defined error.

BUG=angle:773

Change-Id: I1e31756faee2d7734f1fc6cfb086d0e7ec6519bc
Reviewed-on: https://chromium-review.googlesource.com/232966Tested-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Brandon Jones <bajones@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>