Update charted to 0.4.8 and roll

packages/which/lib/src/util.dart

-
-library which.src.util;
-
-import 'dart:async';
-
-/// Transparently call `firstWhere` on a [Stream] or [Iterable].
-// TODO: Remove once https://dartbug.com/ is fixed.
-firstWhere(sequence, test, { orElse() }) => sequence is Iterable ?
-  sequence.firstWhere(test, orElse: orElse) :
-    _streamFirstWhere(sequence, test, orElse: orElse);
-
-Future _streamFirstWhere(Stream stream, test(item), { orElse() }) {
-  var pairs = stream.asyncMap((item) => test(item).then((result) => [item, result]));
-  return pairs.firstWhere((pair) => pair.last, defaultValue: () => [orElse(), null]).then((pair) => pair.first);
-}
-
-/// The identity function simply returns its argument ([x]).
-identity(x) => x;