migrate to sk_sp for SkFontMgr API

Bug: skia:
Change-Id: I1bf2a13537f67938cdc9956080065d10ea0bd1d8
Reviewed-on: https://skia-review.googlesource.com/48740
Commit-Queue: Ben Wagner <bungeman@google.com>
Reviewed-by: Ben Wagner <bungeman@google.com>
17 files changed