src/vs/workbench/api/common/extHostTypes.ts/FileDecoration/validate
class FileDecoration:	static validate(d: FileDecoration): void {
		if (d.badge && d.badge.length !== 1 && d.badge.length !== 2) {
			throw new Error(`The 'badge'-property must be undefined or a short character`);
		}
		if (!d.color && !d.badge && !d.tooltip) {
			throw new Error(`The decoration is empty`);
		}
	}