Add DoneProc to Promise Images

This proc will notify the client when we will no longer call fulfill on
their promise image so that can delete any meta data they needed to store
to be able to complete the fulfill requests.

Bug: skia:
Change-Id: Ife1e6845f221c31ce1ae2c0d2ba5e4c8f0203b74
Reviewed-on: https://skia-review.googlesource.com/114092
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
7 files changed