Fix gles2_conform_test failures when Mac switching to core profile

BUG=635081
TEST=gles2_conform_test on FYI mac bots
R=piman@chromium.org
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2259523002
Cr-Commit-Position: refs/heads/master@{#412681}
6 files changed