Missed IIFE inlining opportunity

Given this code:

``` js
(function() {
var $fun;
var $str;
(function() {
$fun = function(a) {
return console.log(a);
};
$str = "hello";
})();
(function() {
$fun($str);
})();
})();
```

It could be inlined all the way to:

``` js
console.log("hello");
```

However, Closure Compiler today only reduces that to:

``` js
(function() {
var a, b;
(function() {
a = function(a) {
return console.log(a);
};
b = "hello";
})();
a(b);
})();
```