Fix MSVS 2015 compilation of tests
Fix MSVS 2015 compilation of tests

"GLenum" needs to be prefixed to disambiguate between global GLenum
and sh::GLenum.

TEST=compile with MSVS 2015

Change-Id: I31a13c8d410bf32c4d5114c03f4b119aae256778
Reviewed-on: https://chromium-review.googlesource.com/746761
Reviewed-by: Olli Etuaho <38ae6c0e2772a20e8e989f80cb8c99d274e44242@nvidia.com>
Commit-Queue: Olli Etuaho <38ae6c0e2772a20e8e989f80cb8c99d274e44242@nvidia.com>

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