This warning happens on some older versions of the X headers, such
as those present on the current Chromium
linux_chromium_chromeos_rel_ng bots. The default warnings in the GN
build are slightly more strict than in GYP which is why we need to
add some isolated warning disables.

BUG=432959

Change-Id: Id6218780195c59f160adae789305638d3463be9a
Reviewed-on: https://chromium-review.googlesource.com/338424Reviewed-by: Corentin Wallez <cwallez@chromium.org>