Only store width and height on SkPixelRef (last part)

Relanding https://skia-review.googlesource.com/c/14105/
in pieces to try to diagnose problems with the Chrome
roll.

Bug: skia:6535
Change-Id: Iefe4825b9ce9be999baeec8ab7ae6651f1caf451
Reviewed-on: https://skia-review.googlesource.com/14860
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Matt Sarett <msarett@google.com>
6 files changed