code: func (v *Surface) CreateSimilar(content Content, width, height int) *Surface {
  	c := C.cairo_surface_create_similar(v.native(),
  		C.cairo_content_t(content), C.int(width), C.int(height))
  	s := wrapSurface(c)
  	runtime.SetFinalizer(s, (*Surface).destroy)
  	return s
  }
docs: // CreateSimilar is a wrapper around cairo_surface_create_similar().