No code actually uses the right-to-left traversal. All it does is add
unnecessary complexity.

TEST=angle_unittests, angle_end2end_tests
BUG=angleproject:1037

Change-Id: Id15498343538c02c252ef0852f9a00c85ac3c4bb
Reviewed-on: https://chromium-review.googlesource.com/275183Tested-by: Olli Etuaho <oetuaho@nvidia.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>