Adds some writepixels caps methods even though it's not implemented,
just to keep dm from crashing in unexpected places.
Bug: skia:9935
Change-Id: Ia76e5abd8a6c72987658af4f8369efe69f6b685c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/279576
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>