Previously,
  ➜  v8 (master) ✔ ./out.gn/x64.optdebug/d8
  V8 version 6.1.0 (candidate)
  d8> var x = undefined
  undefined
  d8> var [a] = x
  (d8):1: TypeError: Cannot read property 'Symbol(Symbol.iterator)' of undefined
  var [a] = x
            ^
  TypeError: Cannot read property 'Symbol(Symbol.iterator)' of undefined
      at (d8):1:11

Now,
  ➜  v8 (fix-iterator) ✔ ./out.gn/x64.optdebug/d8
  V8 version 6.1.0 (candidate)
  d8> var x = undefined
  undefined
  d8> var [a] = x
  (d8):1: TypeError: x is not iterable
  var [a] = x
            ^
  TypeError: x is not iterable
      at (d8):1:11


Bug: v8:6599, v8:6513
Change-Id: I71287a19166af0289e8f7708b8f41ad003ae87ae
Reviewed-on: https://chromium-review.googlesource.com/571175
Commit-Queue: Sathya Gunasekaran <gsathya@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46723}