TEST=conformance2/glsl3/no-attribute-vertex-shader
TEST=deqp/functional/gles3/instancedrendering

BUG=angleproject:2012

Change-Id: I234410fabf6a8fcd87040c8085ca5dce82fa8932
Reviewed-on: https://chromium-review.googlesource.com/559851
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>