Add constructors to all the event classes.

client/html/src/TextEventWrappingImplementation.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 TextEventWrappingImplementation extends UIEventWrappingImplementation implements TextEvent {
+  TextEventWrappingImplementation._wrap(ptr) : super._wrap(ptr);
+
+  factory TextEventWrappingImplementation(String type, Window view, String data,
+      [bool canBubble = true, bool cancelable = true]) {
+    final e = dom.document.createEvent("TextEvent");
+    e.initTextEvent(type, canBubble, cancelable, LevelDom.unwrap(view), data);
+    return LevelDom.wrapTextEvent(e);
+  }
+
+  String get data() => _ptr.data;
+}