Test WebGL2 on ANGLE's GL backed on Windows/NVIDIA.

TBR=zmo@chromium.org

BUG=693090
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;master.tryserver.chromium.android:android_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2701523005
Cr-Commit-Position: refs/heads/master@{#451851}
3 files changed