Advanced compilation breaks due to lack of __proto__ support?

``` js
// ==ClosureCompiler==
// @compilation_level ADVANCED_OPTIMIZATIONS
// @output_file_name default.js
// @use_closure_library true
// @formatting pretty_print
// ==/ClosureCompiler==

/** @constructor */
function Base() {
}
Base.prototype.x = 1;

/** @constructor @extends {Base} */
function Derived() {
Base.call(this);
}
Derived.prototype = {
__proto__: Base.prototype,
constructor: Derived
};

var d = new Derived;
alert(d.x);
```

This compiles to:

``` js
function a() {
}
a.prototype = {};
alert((new a).x);
```

Which is clearly not right.