Enable PbufferTest on Linux by not advertising bindable configs GLX Pbuffers are not bindable so implementing bindable pbuffers would have to be one of the following: - Implement Pbuffer as GLXPixmaps, with complication arising in the initialization. - Implement Pbuffers as GL textures, which would require a large change of the EGL implementation. - Fake bindable Pbuffers with glCopyTexImage2D, with obvious performance problems. BUG=angleproject:892 Change-Id: I7d9cd5a4aa2d35343244be3cbe55fc1e492f6928 Reviewed-on: https://chromium-review.googlesource.com/273056 Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Tested-by: Corentin Wallez <cwallez@chromium.org>