clang-format: [JS] support free-standing functions again.

This worked initially but was broken by r210887.

Before:
  function outer1(a, b) {
    function inner1(a, b) { return a; } inner1(a, b);
  } function outer2(a, b) { function inner2(a, b) { return a; } inner2(a, b); }

After:
  function outer1(a, b) {
    function inner1(a, b) { return a; }
    inner1(a, b);
  }
  function outer2(a, b) {
    function inner2(a, b) { return a; }
    inner2(a, b);
  }

Thanks to Adam Strzelecki for working on this.