Add un-implemented API for SkDevice::drawCoverageMask

Also adds the staging virtual for SkDevice subclasses to opt into
letting SkCanvas handle mask filters.

Bug: b/304823483
Change-Id: I8d64cda8dc0c2ef8f6db550db222cfd25a11fee5
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/761277
Reviewed-by: Nicolette Prevost <nicolettep@google.com>
Reviewed-by: James Godfrey-Kittle <jamesgk@google.com>
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
2 files changed