extensions/emmet/src/util.ts/iterateCSSToken
export function iterateCSSToken(token: FlatCssToken, fn: (x: any) => any): boolean {
	for (let i = 0, il = token.size; i < il; i++) {
		if (fn(token.item(i)) === false || iterateCSSToken(token.item(i), fn) === false) {
			return false;
		}
	}
	return true;
}