Wrap cached GrTextures in GrTextureProxies (e.g., blur profiles, nine-patch blurs, etc.)

This is pulled out of: https://skia-review.googlesource.com/c/8823/ (Remove GrFragmentProcessor-derived class' GrTexture-based ctors)

Change-Id: I5feac04dc1bf54bd74c65febdf6bba9e7ce28f55
Reviewed-on: https://skia-review.googlesource.com/8942
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
7 files changed