An incorrect check was blocking existing support we added for the
extension.

BUG=angleproject:1226

Change-Id: I335053b1bebb37fd9296b36702031bd34c1bb59e
Reviewed-on: https://chromium-review.googlesource.com/313992
Tryjob-Request: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>