Rename GrDrawOp::xpRequiresDstTexture to finalize and change return type to an enum

Bug: skia:
Change-Id: I0f9d9d3ef1dd20821f171f7d6237491921fbbd97
Reviewed-on: https://skia-review.googlesource.com/20142
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
15 files changed