In TS 3.9, ES2015 output can contain ES classes that are wrapped in an
IIFE. So now ES2015 class declarations can look like one of:
```
class OuterClass1 {}
```
```
let OuterClass = class InnerClass {};
```
```
var AliasClass;
let OuterClass = AliasClass = class InnerClass {};
```
```
let OuterClass = (() => class InnerClass {}};
```
```
var AliasClass;
let OuterClass = AliasClass = (() => class InnerClass {})();
```
```
let OuterClass = (() => {
let AdjacentClass = class InnerClass {};
// ... static properties or decorators attached to `AdjacentClass`
return AdjacentClass;
})();
```
```
var AliasClass;
let OuterClass = AliasClass = (() => {
let AdjacentClass = class InnerClass {};
// ... static properties or decorators attached to `AdjacentClass`
return AdjacentClass;
})();
```
The `Esm5ReflectionHost` already handles slightly different IIFE wrappers
around function-based classes. This can be substantially reused when
fixing `Esm2015ReflectionHost`, since there is a lot of commonality
between the two.
This commit moves code from the `Esm5ReflectionHost` into the `Esm2015ReflectionHost`
and looks to share as much as possible between the two hosts.
PR Close#36989
d7440c452a