Add constructors to all the event classes.

client/html/src/MessageEventWrappingImplementation.dart

Index: client/html/src/MessageEventWrappingImplementation.dart
diff --git a/client/html/generated/src/wrapping/_MessageEventWrappingImplementation.dart b/client/html/src/MessageEventWrappingImplementation.dart
similarity index 70%
rename from client/html/generated/src/wrapping/_MessageEventWrappingImplementation.dart
rename to client/html/src/MessageEventWrappingImplementation.dart
index c196ea95a05af79a401e2637448a2978a9db1c6d..a054559c091804fa0d90b9e4219a9f75de86f159 100644
--- a/client/html/generated/src/wrapping/_MessageEventWrappingImplementation.dart
+++ b/client/html/src/MessageEventWrappingImplementation.dart
@@ -2,11 +2,18 @@
 // 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.
-
 class MessageEventWrappingImplementation extends EventWrappingImplementation implements MessageEvent {
   MessageEventWrappingImplementation._wrap(ptr) : super._wrap(ptr) {}
 
+  factory MessageEventWrappingImplementation(String type, String data,
+      String origin, String lastEventId, Window source, MessagePort port,
+      [bool canBubble = false, bool cancelable = false]) {
+    var e = dom.document.createEvent("MessageEvent");
+    e.initMessageEvent(type, canBubble, cancelable, data, origin, lastEventId,
+        LevelDom.unwrap(source), LevelDom.unwrap(port));
+    return LevelDom.wrapMessageEvent(e);
+  }
+
   String get data() { return _ptr.data; }
 
   String get lastEventId() { return _ptr.lastEventId; }