This has been very useful to figure out the FBConfig story for the GLX
EGL implementation.

BUG=angleproject:892

Change-Id: Icd9afd8e4bdd8766d2fa727afcaf20826c2faf2a
Reviewed-on: https://chromium-review.googlesource.com/272371Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Corentin Wallez <cwallez@chromium.org>