Make SkImage_Gpu be deferred

This CL removes the GrTexture-based ctor forcing everyone to create deferred SkImage_Gpus.

split out into:
https://skia-review.googlesource.com/c/9106/ (Remove atlas creation from GrResourceProvider)

Change-Id: I266bbe089c242fe54d5b7adcc7895aa5a39440a0
Reviewed-on: https://skia-review.googlesource.com/6680
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
15 files changed