Function Inlining loses captures of "super"

[ChadKillingsworth]

Rewriting Async methods produces code such as:

class Foo extends Bar {
  baz() {
    const jscomp$get$super$baz = () => super.baz;
    const jscomp$this = this;
    return function() {
      jscomp$get$super$baz().call(jscomp$this);
    }
  }
}

Currently, function inling will inline the super.baz return value from the arrow function to produce an invalid reference to super. This only seems to show up with ES2015 out as a language.

[MatthewMerrill]

Submitted fix internally