We checked this at link time in the D3D back-end, but this restriction applies to all shaders. TEST=dEQP-GLES2.functional.shaders.fragdata.* BUG=angleproject:995 BUG=478572 Change-Id: I99111cc6aa05b9352693f9c3b5bc70d56c9842d4 Reviewed-on: https://chromium-review.googlesource.com/269846Reviewed-by: Zhenyao Mo <zmo@chromium.org> Tested-by: Jamie Madill <jmadill@chromium.org>
