Reland with a fix for a compilation that happened because of a bad
rebase.

Previously there was a TODO to check if we supported ES3 before setting
the conformant bitfield. Now it is done.

BUG=angleproject:1188

Change-Id: I3ef2bd2bc71fb61c465085d32cf08a633904caa6
Reviewed-on: https://chromium-review.googlesource.com/312271Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Corentin Wallez <cwallez@chromium.org>