Interface blocks no longer allow duplicate fields

bug: skia:12793
Change-Id: Idccdab5ee8f1c7792bdfe98efd379d0199a65377
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/492397
Reviewed-by: John Stiles <johnstiles@google.com>
Commit-Queue: Julia Lavrova <jlavrova@google.com>
3 files changed