Regression test for crbug.com/1140845. Check that a "then" gettter on the object prototype does not crash V8
Evaluating a simple string 'foo' without side-effects should give us the string.
{
    id : <messageId>
    result : {
        result : {
            type : string
            value : foo
        }
    }
}
Evaluating a simple string 'foo' with side-effets should give us the string.
{
    id : <messageId>
    result : {
        result : {
            type : string
            value : foo
        }
    }
}
