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:

Review URL: https://codereview.chromium.org/896163003
37 files changed