hide nested hinting enum

Bug: skia:2664
Bug: skia:8527
Change-Id: I8f4b832d5524fb792bcc608d6bd515229881b048
Reviewed-on: https://skia-review.googlesource.com/c/168270
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
28 files changed