add fontmetrics to custom typeface

Change-Id: Ib6f468f6fd35b73e590d22a33d1322d3de48edb2
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/290645
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
3 files changed