src/vs/workbench/services/userData/browser/userDataInit.ts/UserDataInitializationService/getExtensionsPreviewInitializer
class UserDataInitializationService:	private getExtensionsPreviewInitializer(instantiationService: IInstantiationService): Promise<ExtensionsPreviewInitializer | null> {
		if (!this.extensionsPreviewInitializerPromise) {
			this.extensionsPreviewInitializerPromise = (async () => {
				const userDataSyncStoreClient = await this.createUserDataSyncStoreClient();
				if (!userDataSyncStoreClient) {
					return null;
				}
				const userData = await userDataSyncStoreClient.readResource(SyncResource.Extensions, null);
				return instantiationService.createInstance(ExtensionsPreviewInitializer, userData);
			})();
		}
		return this.extensionsPreviewInitializerPromise;
	}