Revert of Revert "Move DstCopy on gpu into the GrXferProcessor." (patchset #1 id:1 of https://codereview.chromium.org/896163003/)

Reason for revert:
failed on my manual revert

Original issue's description:
> Revert "Move DstCopy on gpu into the GrXferProcessor."
>
> This reverts commit 74a11753604768bf461b80cabb66060e8564d82c.
>
> TBR=joshualitt@google.com,bsalomon@google.com
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=skia:
>
> Committed: https://skia.googlesource.com/skia/+/3e9dfdb3784c0cbfecf7589a74aa9aff7ef40abd

TBR=
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review URL: https://codereview.chromium.org/900913002
37 files changed