Passes:
 * dEQP-GLES3.functional.implementation_limits.num_compressed_texture_formats
 * dEQP-GLES3.functional.implementation_limits.compressed_texture_formats
 * dEQP-GLES3.functional.texture.*eac*
 * dEQP-GLES3.functional.texture.*etc2*

BUG=angleproject:598

Change-Id: Iaec1756b540f8f44c821fd8b9ba63f115ebe6de0
Reviewed-on: https://chromium-review.googlesource.com/305520Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>