Key had an unfortunate association with keyboard input.
This is an API change. The following rewrites were run to fixup
Gio code:
$ gofmt -r 'pointer.InputOp{Key:a} -> pointer.InputOp{Tag:a}' -w .
$ gofmt -r 'pointer.InputOp{Key:a, Grab:b} -> pointer.InputOp{Tag:a, Grab:b}' -w .
$ gofmt -r 'key.InputOp{Key:a} -> key.InputOp{Tag:a}' -w .
$ gofmt -r 'key.InputOp{Key:a, Focus:b} -> key.InputOp{Tag:a, Focus:b}' -w .
$ gofmt -r 'event.Key -> event.Tag' -w .
Signed-off-by: Elias Naur <mail@eliasnaur.com>