If the GL context generates a CONTEXT_LOST error, stop checking for errors.
This error will be generated continuously and result in an infinite loop.

BUG=angleproject:3020

Change-Id: Ib78d1ff3f84103e658307f2f892538700916449d
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2142312Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Geoff Lang <geofflang@chromium.org>