Updated the FenceSync and FenceNV objects to use Error objects. BUG=angle:520 Change-Id: I1e49b35905d8916baadb129c8aa58a11bd721500 Reviewed-on: https://chromium-review.googlesource.com/220781 Reviewed-by: Shannon Woods <shannonwoods@chromium.org> Tested-by: Geoff Lang <geofflang@chromium.org>