Make SkPromiseImageTexture ref counted.

This makes the API easier to use in Chrome.

It is no longer required to pass the SkPromiseImageTexture to the
release proc.

Bug: skia:
Change-Id: I6636401f6a7915d3ad15e890718638bc91a58cc4
Reviewed-on: https://skia-review.googlesource.com/c/183383
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
8 files changed