Add a new invariant declaration operator.

BUG=angle:711

Change-Id: I54a48b636a68c317b8d44ee2d578847b80095289
Reviewed-on: https://chromium-review.googlesource.com/213500
Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>
11 files changed