Revert "migrate to sk_sp for SkFontMgr API"

This reverts commit 4bf296be2821d2bdd0afabae9fdfe18e7e9b59cb.

Reason for revert: need guard for flutter

Original change's description:
> 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>

TBR=bungeman@google.com,reed@google.com

Change-Id: Ib0b2d00fcbcdb6131444f94d1046df6dae24f551
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:
Reviewed-on: https://skia-review.googlesource.com/50940
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
17 files changed