This faciliatates an upcoming change to treat all handle types
uniformly with respect to releasing.

BUG=angleproject:1684

Change-Id: I632262a57b3a447cf4999c28ab359fe931549576
Reviewed-on: https://chromium-review.googlesource.com/442674Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>