I thought these might have different performance characteristics when
compared to the main configs. It's possible they would also need to
forego using SwapBuffers to get different profiles. Right now perf is
pretty similar to with the default FBO.

Bug: angleproject:3117
Change-Id: Ic03b4ebd8c606af5121854565525e37e66f91435
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1650785
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>