The intent was already to enable it but without glEnable(GL_DEBUG_OUTPUT)
the Linux NVIDIA driver doesn't output anything.

BUG=

Change-Id: Ia9a500c2e792ee7c4e2a7be60d478419eda617e1
Reviewed-on: https://chromium-review.googlesource.com/385278
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>