Remove stale files from lib/html/src.

lib/html/src/StorageEventWrappingImplementation.dart

-// Copyright (c) 2011, 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 StorageEventWrappingImplementation extends EventWrappingImplementation implements StorageEvent {
-  StorageEventWrappingImplementation._wrap(ptr) : super._wrap(ptr);
-
-  factory StorageEventWrappingImplementation(String type, String key,
-      String url, Storage storageArea, [bool canBubble = true,
-      bool cancelable = true, String oldValue = null,
-      String newValue = null]) {
-    final e = dom.document.createEvent("StorageEvent");
-    e.initStorageEvent(type, canBubble, cancelable, key, oldValue, newValue,
-        url, LevelDom.unwrap(storageArea));
-    return LevelDom.wrapStorageEvent(e);
-  }
-
-  String get key() => _ptr.key;
-
-  String get newValue() => _ptr.newValue;
-
-  String get oldValue() => _ptr.oldValue;
-
-  Storage get storageArea() => LevelDom.wrapStorage(_ptr.storageArea);
-
-  String get url() => _ptr.url;
-}