Until the driver implementation completes, use a different name for the
unreleased extension (tagged with GOOGLEX instead of EXT).

Bug: chromium:1088005
Change-Id: I0b948c9c82825681ab130ae3dd91026ea6cb57cf
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2795041Reviewed-by: David Reveman <reveman@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>