Fill in some missing virtuals from canvas subclasses

Bug: skia:
Change-Id: If7306fa6c5a1619952e1159e6ebca8f04b4d9c8e
Reviewed-on: https://skia-review.googlesource.com/113262
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
5 files changed