shiny/driver/x11driver: optimize simple copies and scales.
shiny/driver/x11driver: optimize simple copies and scales.

Change-Id: Ia4c8cf18e813953ee38becaa8af24fe663097e8b
Reviewed-on: https://go-review.googlesource.com/16030
Reviewed-by: David Crawshaw <a2f0bf29257797dd66800b4fbb9945c3e216c004@golang.org>

AkihiroSuda/golang-exp-aspectgo,JamesDunne/exp,golang/exp,AkihiroSuda/golang-exp-aspectgo,golang/exp,AkihiroSuda/golang-exp-aspectgo,JamesDunne/exp,golang/exp