src/vs/workbench/contrib/localization/browser/localeService.ts/WebLocaleService/setLocale
class WebLocaleService:	async setLocale(languagePackItem: ILanguagePackItem): Promise<void> {
		const locale = languagePackItem.id;
		if (locale === Language.value() || (!locale && Language.value() === navigator.language)) {
			return;
		}
		if (locale) {
			window.localStorage.setItem('vscode.nls.locale', locale);
		} else {
			window.localStorage.removeItem('vscode.nls.locale');
		}

		const restartDialog = await this.dialogService.confirm({
			type: 'info',
			message: localize('relaunchDisplayLanguageMessage', "To change the display language, {0} needs to reload", this.productService.nameLong),
			detail: localize('relaunchDisplayLanguageDetail', "Press the reload button to refresh the page and set the display language to {0}.", languagePackItem.label),
			primaryButton: localize({ key: 'reload', comment: ['&& denotes a mnemonic character'] }, "&&Reload"),
		});

		if (restartDialog.confirmed) {
			this.hostService.restart();
		}
	}