glmark2 uses the visual id, which is discarded in angle.  This change
retrieves these ids from X11 and stores them in the egl::Config.

Bug: angleproject:3125
Change-Id: I2b524ecb71d675efa01cc9100a3dfe6fd57913f0
Reviewed-on: https://chromium-review.googlesource.com/c/1450221Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Frank Henigman <fjhenigman@chromium.org>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>