serialize fonts instead of paints

Some changes from before:
- we don't force serializing a typeface if the field is null
- we don't serialize the blob bounds (don't trust them)

Bug: skia:
Change-Id: I41281b2aa63a1026de87330023346f1da5378c1f
Reviewed-on: https://skia-review.googlesource.com/c/179735
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
Reviewed-by: Herb Derby <herb@google.com>
7 files changed