UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/64.0.3282.140 Safari/537.36

Steps to reproduce the problem:
1. run `new Set(123);`
2. run `for (const x of 123);`

What is the expected behavior?
It would be nice if the error message generated by passing something that is not an iterator would match the error messages generated by for-of loops in similar situations.

What went wrong?
Nothing here is explicitly wrong, but it looks like 2 very similar errors both of which are the result of hitting the same case in the spec (https://tc39.github.io/ecma262/#sec-getiterator step 2), result in different messages.
`
The message generated by the for-of loop `Uncaught TypeError: 123 is not iterable` is much more intuitive and actionable than the message generated by the Set constructor (`Uncaught TypeError: undefined is not a function`).

It looks like v8 is probably trapping errors generated by calling getIterator (https://tc39.github.io/ecma262/#sec-runtime-semantics-forin-div-ofheadevaluation-tdznames-expr-iterationkind steb 7.b)

While the set constructor does not, and just lets the error bubble up without any special casing.

Did this work before? No 

Chrome version: 64.0.3282.140  Channel: stable
OS Version: OS X 10.13.3
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