Add a new entry point for making promise images

This paves the way for promise image sharing among direct & recording
contexts, and untethers promise images from DDL recorder.

Followup CLs will migrate us to actually use this entry point,
and then migrate Chrome to do same.

Bug: skia:10286
Change-Id: I0ad46e8e4b91d8bc03cb039b304d2ea6d8a65c35
Commit-Queue: Brian Salomon <>
Reviewed-by: Brian Salomon <>
Reviewed-by: Robert Phillips <>
12 files changed