This will save us some time on D3D11 startup.

BUG=angleproject:1014

Change-Id: Ic00b3dfd9f6230d2d54e6e9bb74be55b923697fe
Reviewed-on: https://chromium-review.googlesource.com/275775Tested-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Brandon Jones <bajones@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>