Array.prototype.slice and Array.prototype.splice should not call user defined valueOf of start, end arguments more than once

[].slice({valueOf:function(){print("get-start")}}, {valueOf:function(){print("get-end")}})

=> prints "get-start|end" twice but should only be once

[].splice({valueOf:function(){print("get-start")}})

=> prints "get-start" twice but should only be once