src/vs/workbench/api/browser/mainThreadDocuments.ts/MainThreadDocuments/_doCreateUntitled
class MainThreadDocuments:	private _doCreateUntitled(associatedResource?: URI, mode?: string, initialValue?: string): Promise<URI> {
		return this._textFileService.untitled.resolve({
			associatedResource,
			mode,
			initialValue
		}).then(model => {
			const resource = model.resource;

			if (!this._modelIsSynced.has(resource)) {
				throw new Error(`expected URI ${resource.toString()} to have come to LIFE`);
			}

			this._proxy.$acceptDirtyStateChanged(resource, true); // mark as dirty

			return resource;
		});
	}