src/vs/workbench/api/common/extHostLocalizationService.ts/ExtHostLocalizationService/getBundleLocation
class ExtHostLocalizationService:	private async getBundleLocation(extension: IExtensionDescription): Promise<URI | undefined> {
		if (extension.isBuiltin) {
			const uri = await this._proxy.$fetchBuiltInBundleUri(extension.identifier.value);
			return URI.revive(uri);
		}

		return extension.l10n
			? URI.joinPath(extension.extensionLocation, extension.l10n, `bundle.l10n.${this.currentLanguage}.json`)
			: undefined;
	}