Update charted to 0.4.8 and roll

packages/collection/lib/src/equality_map.dart

+// 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.
+
+import 'dart:collection';
+
+import 'equality.dart';
+import 'wrappers.dart';
+
+/// A [Map] whose key equality is determined by an [Equality] object.
+class EqualityMap<K, V> extends DelegatingMap<K, V> {
+  /// Creates a map with equality based on [equality].
+  EqualityMap(Equality<K> equality)
+      : super(new LinkedHashMap(
+            equals: equality.equals,
+            hashCode: equality.hash,
+            isValidKey: equality.isValidKey));
+
+  /// Creates a map with equality based on [equality] that contains all
+  /// key-value pairs of [other].
+  ///
+  /// If [other] has multiple keys that are equivalent according to [equality],
+  /// the last one reached during iteration takes precedence.
+  EqualityMap.from(Equality<K> equality, Map<K, V> other)
+      : super(new LinkedHashMap(
+            equals: equality.equals,
+            hashCode: equality.hash,
+            isValidKey: equality.isValidKey)) {
+    addAll(other);
+  }
+}