This will facilitate changes for WebGL compatibility.

BUG=angleproject:747
BUG=angleproject:1708

Change-Id: I62e5d684ca10a843b5e958afe9954c1065bfeb19
Reviewed-on: https://chromium-review.googlesource.com/442093Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>