fix links and missing constructor

Docs-Preview: https://skia.org/?cl=31145
Bug: skia: 6898
Change-Id: Ic94a15551f3683d9de5d3bda53394d2efce0d6a4
Reviewed-on: https://skia-review.googlesource.com/31145
Commit-Queue: Cary Clark <caryclark@skia.org>
Reviewed-by: Cary Clark <caryclark@skia.org>
6 files changed