Add refcnt'ed immutable vertices class for SkCanvas::drawVertices.

Change-Id: I44a62f5efc674d0adbbf4a33690c3ded9fab3803
Reviewed-on: https://skia-review.googlesource.com/8040
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
20 files changed