Class decorator causes static method to be removed when compiled in advanced mode

This Typescript source:

```
function decorate(target: any) { }

@decorate
class StaticTest {
private static testMethod() {
console.log('I am missing');
}

private invokesTest = () => StaticTest.testMethod();

constructor() {
this.invokesTest();
}
}
```

Gets transpiled (ES2017 target) into:

```
var __decorate = (this && this.__decorate) || function (decorators, target, key, desc) {
var c = arguments.length, r = c < 3 ? target : desc === null ? desc = Object.getOwnPropertyDescriptor(target, key) : desc, d;
if (typeof Reflect === "object" && typeof Reflect.decorate === "function") r = Reflect.decorate(decorators, target, key, desc);
else for (var i = decorators.length - 1; i >= 0; i--) if (d = decorators[i]) r = (c < 3 ? d(r) : c > 3 ? d(target, key, r) : d(target, key)) || r;
return c > 3 && r && Object.defineProperty(target, key, r), r;
};
var StaticTest_1;
"use strict";
function decorate(target) { }
let StaticTest = StaticTest_1 = class StaticTest {
constructor() {
this.invokesTest = () => StaticTest_1.testMethod();
this.invokesTest();
}
static testMethod() {
console.log('I am missing');
}
};
StaticTest = StaticTest_1 = __decorate([
decorate
], StaticTest);
```

Which gets CCed (with `ADVANCED_MODE`) into:

```
var l = this && this.c || function(h, b, d, e) {
var f = arguments.length, a = 3 > f ? b : null === e ? e = Object.getOwnPropertyDescriptor(b, d) : e, g;
if ("object" === typeof Reflect && "function" === typeof Reflect.a) {
a = Reflect.a(h, b, d, e);
} else {
for (var k = h.length - 1; 0 <= k; k--) {
if (g = h[k]) {
a = (3 > f ? g(a) : 3 < f ? g(b, d, a) : g(b, d)) || a;
}
}
}
return 3 < f && a && Object.defineProperty(b, d, a), a;
}, m;
"use strict";
var n = m = function() {
this.b = function() {
m.f();
};
this.b();
};
n = m = l([function() {
}], n);
```

The static method that prints "I am missing" is gone.

Same thing happens when the decorator is called as a function (i.e., `decorate(StaticTest)`.

`@nocollapse` prevents that from happening but it's easy to forget to add it =>
runtime errors.

Hey and thanks so much for all the work you guys do on Closure Compiler!