change paint serialization to exclude font-related fields

This is slightly preemptive, since paint still has getters/setters for
these fields, but skia no longer looks at them, so...

Reduces serial size by 20-bytes + size of a typeface

Bug: skia:2664
Change-Id: If1997c823db5b3d83b04cb7e1bc1d6787795b70a
Reviewed-on: https://skia-review.googlesource.com/c/181174
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
5 files changed