[ngatoy] Delegate creation of the sort key to the individual Cmds

Bug: skia:11837
Change-Id: I4fa19c46b38659d160de92de90e80a23ee8e5fcc
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/415461
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
4 files changed