Make Storage implement Map.

lib/html/dartium/html_dartium.dart

Index: lib/html/dartium/html_dartium.dart
diff --git a/lib/html/dartium/html_dartium.dart b/lib/html/dartium/html_dartium.dart
index 1a8e35d3a5862a7129cdb725a195f49c26964e14..da0d379f031e32a4292bf50ff0552e6694c24712 100644
--- a/lib/html/dartium/html_dartium.dart
+++ b/lib/html/dartium/html_dartium.dart
@@ -18388,8 +18388,54 @@ class _SpeechRecognitionResultListImpl extends _DOMTypeBase implements SpeechRec
     return _wrap(_ptr.item(_unwrap(index)));
   }
 }
+// Copyright (c) 2012, 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.
 
 class _StorageImpl extends _DOMTypeBase implements Storage {
+
+  // TODO(nweiz): update this when maps support lazy iteration
+  bool containsValue(String value) => getValues().some((e) => e == value);
+
+  bool containsKey(String key) => getItem(key) != null;
+
+  String operator [](String key) => getItem(key);
+
+  void operator []=(String key, String value) => setItem(key, value);
+
+  String putIfAbsent(String key, String ifAbsent()) {
+    if (!containsKey(key)) this[key] = ifAbsent();
+    return this[key];
+  }
+
+  String remove(String key) {
+    final value = this[key];
+    removeItem(key);
+    return value;
+  }
+
+  void forEach(void f(String key, String value)) {
+    for (var i = 0; true; i++) {
+      final key = key(i);
+      if (key == null) return;
+
+      f(key, this[key]);
+    }
+  }
+
+  Collection<String> getKeys() {
+    final keys = [];
+    forEach((k, v) => keys.add(k));
+    return keys;
+  }
+
+  Collection<String> getValues() {
+    final values = [];
+    forEach((k, v) => values.add(v));
+    return values;
+  }
+
+  bool isEmpty() => key(0) == null;
   _StorageImpl._wrap(ptr) : super._wrap(ptr);
 
   int get length() => _wrap(_ptr.length);
@@ -18416,6 +18462,7 @@ class _StorageImpl extends _DOMTypeBase implements Storage {
     _ptr.setItem(_unwrap(key), _unwrap(data));
     return;
   }
+
 }
 
 class _StorageEventImpl extends _EventImpl implements StorageEvent {
@@ -33759,9 +33806,8 @@ interface SpeechRecognitionResultList {
 // 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.
 
-// WARNING: Do not edit - generated code.
-
-interface Storage {
+interface Storage extends Map<String, String> {
+/*
 
   final int length;
 
@@ -33774,6 +33820,8 @@ interface Storage {
   void removeItem(String key);
 
   void setItem(String key, String data);
+
+*/
 }
 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a