src/vs/workbench/api/browser/mainThreadDialogs.ts/MainThreadDialogs/$showSaveDialog
class MainThreadDialogs:	async $showSaveDialog(options?: MainThreadDialogSaveOptions): Promise<URI | undefined> {
		const convertedOptions = MainThreadDialogs._convertSaveOptions(options);
		if (!convertedOptions.defaultUri) {
			convertedOptions.defaultUri = await this._fileDialogService.defaultFilePath();
		}
		return Promise.resolve(this._fileDialogService.showSaveDialog(convertedOptions));
	}