Add constructors to all the event classes.

client/html/src/ProgressEventWrappingImplementation.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.
 
-// WARNING: Do not edit - generated code.
-
 class ProgressEventWrappingImplementation extends EventWrappingImplementation implements ProgressEvent {
   ProgressEventWrappingImplementation._wrap(ptr) : super._wrap(ptr) {}
 
+  factory ProgressEventWrappingImplementation(String type, int loaded,
+      [bool canBubble = false, bool cancelable = false,
+      bool lengthComputable = false, int total = 0]) {
+    var e = dom.document.createEvent("ProgressEvent");
+    e.initProgressEvent(type, canBubble, cancelable, lengthComputable, loaded,
+        total);
+    return LevelDom.wrapProgressEvent(e);
+  }
+
   bool get lengthComputable() { return _ptr.lengthComputable; }
 
   int get loaded() { return _ptr.loaded; }
 
   int get total() { return _ptr.total; }
-
-  void initProgressEvent(String typeArg, bool canBubbleArg, bool cancelableArg, bool lengthComputableArg, int loadedArg, int totalArg) {
-    _ptr.initProgressEvent(typeArg, canBubbleArg, cancelableArg, lengthComputableArg, loadedArg, totalArg);
-    return;
-  }
 }