If ANGLE is using instanced point sprites (e.g. on Feature Level 9_3) then it
still tries to compile the point sprite geometry shader. It shouldn't do this.

Change-Id: I6e7753dd337c385893fc4bea6c8438aeaf5e8427
Reviewed-on: https://chromium-review.googlesource.com/321397
Tryjob-Request: Austin Kinross <aukinros@microsoft.com>
Tested-by: Austin Kinross <aukinros@microsoft.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>