Realization of String.prototype.split is inconsistent with ecma-262

Hello, executing following code:

let arg_0 = /(.)\1/i;
let handler_0 = {get:function (oTarget, sKey) { 
    print(sKey.toString());
    return Reflect.get(oTarget, sKey); 
}};
var p_0 = new Proxy(arg_0, handler_0);
(0 + "\u1234\0").split(p_0);

In ecma-262, seperator’s Symbol.split should be got firstly. However, ch get Symbol.toPrimitive firstly.

Output of ch:

Symbol(Symbol.toPrimitive)
toString
TypeError: RegExp.prototype.toString: 'this' is not a RegExp object

Output of other engines:

Symbol(Symbol.split)
constructor
flags
Symbol(Symbol.match)
source

BT group 2018.09.10

[jackhorton]

I feel like we should just take the jump and enable all of the ES6 bits at this point…

[rhuanjl]

Consolidating as part of #6390