Already limited by IMPLEMENTATION_MAX_ACTIVE_TEXTURES,
but Nexus 5X doesn't support that many.

BUG=angleproject:2314

Change-Id: I43b530ba25e9cf7055e74525f479fb10cc7394a2
Reviewed-on: https://chromium-review.googlesource.com/882443
Commit-Queue: Yuly Novikov <ynovikov@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>