The patch changes CallPrinter's AST traversal to continue even after
the first positive match for an AST node. This helps us check for the
subsequent GetIterator AST node in case of destructuring.

We can not differentiate between the function call failing and the
GetIterator failing based on source position info. This would involve
runtime checks costing performance.

Instead of providing an incorrect error, we provide both the
possiblities to user and allow them to disambiguate.

Previously,
  d8> function f() { return 5; }
  undefined
  d8> var [a] = f();
  (d8):1: TypeError: f is not a function
  var [a] = f();
            ^
  TypeError: f is not a function
      at (d8):1:11


Now,
  d8> function f() { return 5; }
  undefined
  d8> var [a] = f();
  (d8):1: TypeError: f is not a function or its return value is not iterable
  var [a] = f();
            ^
  TypeError: f is not a function or its return value is not iterable
      at (d8):1:11

Bug: v8:6616, v8:6513
Change-Id: I3d6427f10cae54951b0ad0e5ddcbe802bb7191c1
Reviewed-on: https://chromium-review.googlesource.com/594894
Commit-Queue: Sathya Gunasekaran <gsathya@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47025}