Currently there is no way to specify the data that is bound to them.
That will come in later changes.
Bug: skia:12720
Change-Id: I3301a825486469396a13a4095b66d9e0b81f183b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/543716
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>