Update charted to 0.4.8 and roll

packages/collection/test/combined_wrapper/map_test.dart

+// Copyright (c) 2017, 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 'package:collection/collection.dart';
+import 'package:test/test.dart';
+
+import '../unmodifiable_collection_test.dart' as common;
+
+void main() {
+  var map1 = const {1: 1, 2: 2, 3: 3};
+  var map2 = const {4: 4, 5: 5, 6: 6};
+  var map3 = const {7: 7, 8: 8, 9: 9};
+  var concat = {}..addAll(map1)..addAll(map2)..addAll(map3);
+
+  // In every way possible this should test the same as an UnmodifiableMapView.
+  common.testReadMap(
+      concat, new CombinedMapView([map1, map2, map3]), 'CombinedMapView');
+
+  common.testReadMap(
+      concat,
+      new CombinedMapView([map1, {}, map2, {}, map3, {}]),
+      'CombinedMapView (some empty)');
+
+  test('should function as an empty map when no maps are passed', () {
+    var empty = new CombinedMapView([]);
+    expect(empty, isEmpty);
+    expect(empty.length, 0);
+  });
+
+  test('should function as an empty map when only empty maps are passed', () {
+    var empty = new CombinedMapView([{}, {}, {}]);
+    expect(empty, isEmpty);
+    expect(empty.length, 0);
+  });
+
+  test('should reflect underlying changes back to the combined map', () {
+    var backing1 = <int, int>{};
+    var backing2 = <int, int>{};
+    var combined = new CombinedMapView([backing1, backing2]);
+    expect(combined, isEmpty);
+    backing1.addAll(map1);
+    expect(combined, map1);
+    backing2.addAll(map2);
+    expect(combined, new Map.from(backing1)..addAll(backing2));
+  });
+
+  test('should reflect underlying changes with a single map', () {
+    var backing1 = <int, int>{};
+    var combined = new CombinedMapView([backing1]);
+    expect(combined, isEmpty);
+    backing1.addAll(map1);
+    expect(combined, map1);
+  });
+}