refFoo variant for getters that naturally have a sk_sp

BUG=skia:

Change-Id: I13afa1b81e8a72d93e45fb4d37228be196b0f388
Reviewed-on: https://skia-review.googlesource.com/6923
Reviewed-by: Florin Malita <fmalita@chromium.org>
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Mike Reed <reed@google.com>
19 files changed