Previous patches enable us to get rid of this workaround. We should
in subsequent patches also try to clean up code that uses the
internal Renderer-only version of the context caps.

BUG=angle:789

Change-Id: Ic054090303cdc3f7ee8e45e4577c157559955472
Reviewed-on: https://chromium-review.googlesource.com/227714Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Brandon Jones <bajones@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>