Plumb more SkPaintFilterCanvas virtuals

SkNWayCanvas cannot support virtuals which imply one-to-one proxying,
but SkPaintFilterCanvas can (and should).

Change-Id: If966aa4ec3fcc79e6355a82cc299fd1877e4cf53
Reviewed-on: https://skia-review.googlesource.com/58842
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
4 files changed