Switch GrYUVProvider over to GrTextureProxies

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

Change-Id: I302e6b4c1ffed449a990288ec06f2dfdcdadf1f8
Reviewed-on: https://skia-review.googlesource.com/9448
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
9 files changed