Do not propagate OVR_multiview extension directive The patch fixes the bug of having the OVR_multiview extension directive being outputted by the ESSL translator whenever the SH_INITIALIZE_BUILTINS_FOR_INSTANCED_MULTIVIEW option is enabled. The directive should not be outputted because the extension is emulated through that option. BUG=angleproject:2062 TEST=angle_unittests Change-Id: I95d0a651ace6db42d496de08e774ec7ceca4c197 Reviewed-on: https://chromium-review.googlesource.com/558981 Commit-Queue: Olli Etuaho <oetuaho@nvidia.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>