Move glyph cache and descriptor functions off of SkPaint

BUG=skia:7515

Change-Id: If17b157db1077a9a3c0f9efd03929f62a3486419
Reviewed-on: https://skia-review.googlesource.com/98841
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Herb Derby <herb@google.com>
10 files changed