src/vs/workbench/services/extensions/browser/webWorkerExtensionHost.ts/WebWorkerExtensionHost/start
class WebWorkerExtensionHost:	public async start(): Promise<IMessagePassingProtocol> {
		if (!this._protocolPromise) {
			this._protocolPromise = this._startInsideIframe();
			this._protocolPromise.then(protocol => this._protocol = protocol);
		}
		return this._protocolPromise;
	}