This is the initial draft of a spec that extends
EGL_EXT_platform_base to allow choosing a particular ANGLE D3D
backend.

Change-Id: I1d80fa8b3c4a59fe998f6d15aa0f393bdb9d26c1
Reviewed-on: https://chromium-review.googlesource.com/184975Reviewed-by: Nicolas Capens <nicolascapens@chromium.org>
Commit-Queue: Scott Graham <scottmg@chromium.org>
Tested-by: Scott Graham <scottmg@chromium.org>
(cherry picked from commit dc18dc30)
Reviewed-on: https://chromium-review.googlesource.com/190026Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Shannon Woods <shannonwoods@chromium.org>