Update charted to 0.4.8 and roll

packages/observable/lib/src/change_record.dart

Index: packages/observable/lib/src/change_record.dart
diff --git a/packages/observable/lib/src/change_record.dart b/packages/observable/lib/src/change_record.dart
new file mode 100644
index 0000000000000000000000000000000000000000..b4c4f2457300967b241265910f1356df794e7050
--- /dev/null
+++ b/packages/observable/lib/src/change_record.dart
@@ -0,0 +1,9 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library observable.src.change_record;
+
+/// Records a change to an [Observable].
+// TODO(jmesserly): remove this type
+abstract class ChangeRecord {}