It is not referenced outside of the d3d classes.

BUG=angleproject:884

Change-Id: Ibeec034b1b78b569bea2f1c77d6a686b58b8e010
Reviewed-on: https://chromium-review.googlesource.com/288582Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>