`main()` function used to be needed to support dart, since dart
Does not allow top level statements. Since we no longer use dart
The need for `main()` has been removed.
In preparation for `Basel` and standardized way of running tests
we are removing `main()`
PR Close#21053
BREAKING CHANGE
It is no longer possible to declare classes in this format.
```
Component({...}).
Class({
constructor: function() {...}
})
```
This format would only work with JIT and with ES5. This mode doesn’t
allow build tools like Webpack to process and optimize the code, which
results in prohibitively large bundles. We are removing this API
because we are trying to ensure that everyone is on the fast path by
default, and it is not possible to get on the fast path using the ES5
DSL. The replacement is to use TypeScript and `@Decorator` format.
```
@Component({...})
class {
constructor() {...}
}
```
Miško Hevery
Jason Aden