Remove unnecessary ifdef APPLE from built-in emulation The emulation is already toggled by a compilation flag, so having it behind an ifdef only adds unnecessary complexity, particularly when testing changes to the emulation code. BUG=angleproject:865 Change-Id: Idf7854c2b5323609880b527ed806440dcc8ac091 Reviewed-on: https://chromium-review.googlesource.com/256365 Tested-by: Olli Etuaho <oetuaho@nvidia.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Zhenyao Mo <zmo@chromium.org>