[test-grid] use "max-stride" rather than setting width or height to 0
[test-grid] use "max-stride" rather than setting width or height to 0

pwithnall/mx,clutter-project/mx,pwithnall/mx,pwithnall/mx,jonnylamb/mx,pwithnall/mx,clutter-project/mx,jonnylamb/mx,clutter-project/mx,jonnylamb/mx,jonnylamb/mx,clutter-project/mx