pre-api change, preparing for expanding metadata

Bug: skia:
Change-Id: I367c728172f24166fb7f06a6e22fe37adb8adc4f
Reviewed-on: https://skia-review.googlesource.com/84880
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
3 files changed