Can't Freeze Enum With Namespace

Currently this [compiles without warnings](https://closure-compiler.appspot.com/home#code%3D%252F%252F%2520%253D%253DClosureCompiler%253D%253D%250A%252F%252F%2520%2540output_file_name%2520default.js%250A%252F%252F%2520%2540compilation_level%2520ADVANCED_OPTIMIZATIONS%250A%252F%252F%2520%253D%253D%252FClosureCompiler%253D%253D%250A%250Agoog.provide('foo.Animals')%253B%250A%250A%252F**%250A%2520*%2520%2540enum%250A%2520*%252F%250Afoo.Animals%2520%253D%2520%257B%250A%2520%2520DOG%253A%25200%252C%250A%2520%2520CAT%253A%25201%250A%257D%253B%250A%250Aconst%2520DOG%2520%253D%2520foo.Animals.DOG%253B):

```javascript
goog.provide('foo.Animals');

/**
* @enum
*/
foo.Animals = {
DOG: 0,
CAT: 1
};

const DOG = foo.Animals.DOG;
```

But this [has several warnings](https://closure-compiler.appspot.com/home#code%3D%252F%252F%2520%253D%253DClosureCompiler%253D%253D%250A%252F%252F%2520%2540output_file_name%2520default.js%250A%252F%252F%2520%2540compilation_level%2520ADVANCED_OPTIMIZATIONS%250A%252F%252F%2520%253D%253D%252FClosureCompiler%253D%253D%250A%250Agoog.provide('foo.Animals')%253B%250A%250A%252F**%250A%2520*%2520%2540enum%250A%2520*%252F%250Afoo.Animals%2520%253D%2520Object.freeze(%257B%250A%2520%2520DOG%253A%25200%252C%250A%2520%2520CAT%253A%25201%250A%257D)%253B%250A%250Aconst%2520DOG%2520%253D%2520foo.Animals.DOG%253B):

```javascript
goog.provide('foo.Animals');

/**
* @enum
*/
foo.Animals = Object.freeze({
DOG: 0,
CAT: 1
});

const DOG = foo.Animals.DOG;
```

These are the warnings:

```
JSC_TYPE_MISMATCH: assignment to property Animals of foo
found : {CAT: number, DOG: number}
required: enum{foo.Animals} at line 6 character 0
foo.Animals = Object.freeze({
^
JSC_ENUM_INITIALIZER_NOT_ENUM: enum initializer must be an object literal or an enum at line 6 character 0
foo.Animals = Object.freeze({
^
JSC_INEXISTENT_ENUM_ELEMENT: element DOG does not exist on this enum at line 11 character 12
const DOG = foo.Animals.DOG;
```

This can be worked around by freezing the enum after it is initialized, but doing it all in one go is cleaner syntactically.