Should have been specified for OpenGL instead of D3D11.

Bug: chromium:967796
Change-Id: I099ab51709f69e7abb7fe698e6010241bdccb4bf
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1635751Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>