Revert "Remove unmodifiable map wrappers that could instead use UnmodifiableMapView."

pkg/template_binding/test/custom_element_bindings_test.dart

Index: pkg/template_binding/test/custom_element_bindings_test.dart
diff --git a/pkg/template_binding/test/custom_element_bindings_test.dart b/pkg/template_binding/test/custom_element_bindings_test.dart
index d015825592fc8a17b888960e7cb378558e0a17c2..62fb8ee24e12b6a33f514301973d54c73cffb19b 100644
--- a/pkg/template_binding/test/custom_element_bindings_test.dart
+++ b/pkg/template_binding/test/custom_element_bindings_test.dart
@@ -215,18 +215,34 @@ class WithAttrsCustomElement extends HtmlElement {
 }
 
 // TODO(jmesserly): would be nice to use mocks when mirrors work on dart2js.
-class AttributeMapWrapper<K, V> extends MapView<K, V> {
+class AttributeMapWrapper<K, V> implements Map<K, V> {
   final List log = [];
+  Map<K, V> _map;
 
-  AttributeMapWrapper(Map map) : super(map);
+  AttributeMapWrapper(this._map);
+
+  bool containsValue(Object value) => _map.containsValue(value);
+  bool containsKey(Object key) => _map.containsKey(key);
+  V operator [](Object key) => _map[key];
 
   void operator []=(K key, V value) {
     log.add(['[]=', key, value]);
-    super[key] = value;
+    _map[key] = value;
   }
 
+  V putIfAbsent(K key, V ifAbsent()) => _map.putIfAbsent(key, ifAbsent);
+
   V remove(Object key) {
     log.add(['remove', key]);
-    super.remove(key);
+    _map.remove(key);
   }
+
+  void addAll(Map<K, V> other) => _map.addAll(other);
+  void clear() => _map.clear();
+  void forEach(void f(K key, V value)) => _map.forEach(f);
+  Iterable<K> get keys => _map.keys;
+  Iterable<V> get values => _map.values;
+  int get length => _map.length;
+  bool get isEmpty => _map.isEmpty;
+  bool get isNotEmpty => _map.isNotEmpty;
 }