This speeds up the simple perf test, but it is a very simple
optimization that does not have a cache of pipelines or anything
sophisticated.

BUG=angleproject:1898

Change-Id: Iec126bc73bf28f8bb33662a2f70670588f010d72
Reviewed-on: https://chromium-review.googlesource.com/444850Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>