change private alloc methods to also take fonts

Bug: skia:2664
Change-Id: I772534179ce0c948984640f9fffc22e0372fce97
Reviewed-on: https://skia-review.googlesource.com/c/174848
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Mike Reed <reed@google.com>
7 files changed