[graphite] Merge Resource and ResourceRef together.

There really isn't anything we are gaining from keeping these class
separate. Originally the model was copied when porting over from Ganesh,
but I believe even in Ganesh the split mostly exists because GrResource
use to be public and we friended classes in it.. Since Resource is
internal and there are no plans to friend classes, the split is not
adding much value and just adds extra coding hopes.

Bug: skia:12754
Change-Id: I2e94b459d82b9295fa8450a94c612c593337fb98
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/508676
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
3 files changed