src/vs/workbench/services/outline/browser/outlineService.ts/OutlineService/registerOutlineCreator
class OutlineService:	registerOutlineCreator(creator: IOutlineCreator<any, any>): IDisposable {
		const rm = this._factories.push(creator);
		this._onDidChange.fire();
		return toDisposable(() => {
			rm();
			this._onDidChange.fire();
		});
	}