Also sort enums in getQualifierString in the same order as in the enum
definition.

BUG=angleproject:999
TEST=WebGL conformance tests with --gl-shader-interm-output

Change-Id: I31aa2e4b2405a090f560bf4140d9ee66271e526c
Reviewed-on: https://chromium-review.googlesource.com/269941Tested-by: Olli Etuaho <oetuaho@nvidia.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>