More SkVertices implementation work

- change virtuals to take const SkVertices*, as we do for TextBobs and Images
- override onDrawVerticesObject in recording canvases
- deserialize raw-vertices into SkVertices object

Possibly a follow-on would intercept the raw-form directly in canvas,
and remove the virtual, and only support the object form.

BUG=skia:6366

Change-Id: I57a932667ccb3b3b004beb802ac3ae6898e3c6e0
Reviewed-on: https://skia-review.googlesource.com/9633
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
24 files changed