Web updates

Web IDL a395a59dcfa6

Remove a check for array index in [[Set]] Array index properties are not special on objects with named setters. Note that the corresponding step in [[DefineOwnProperty]] does not have this condition. This change does not affect normal usage; it is only detectable by messing with the prototype of the object. Gecko and WebKit already handle array indexes the same way as other properties; Chrome does for DOMStringMap but does not for Storage. (In the Storage case, it does the exact opposite of the current specification.)