Add constructors to all the event classes.

client/html/src/PageTransitionEventWrappingImplementation.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 PageTransitionEventWrappingImplementation extends EventWrappingImplementation implements PageTransitionEvent {
+  PageTransitionEventWrappingImplementation._wrap(ptr) : super._wrap(ptr);
 
-class PageTransitionEventWrappingImplementation extends EventWrappingImplementation implements PageTransitionEvent {
-  PageTransitionEventWrappingImplementation._wrap(ptr) : super._wrap(ptr) {}
+  factory PageTransitionEventWrappingImplementation(String type,
+      [bool canBubble = true, bool cancelable = true,
+      bool persisted = false]) {
+    final e = dom.document.createEvent("PageTransitionEvent");
+    e.initPageTransitionEvent(type, canBubble, cancelable, persisted);
+    return LevelDom.wrapPageTransitionEvent(e);
+  }
 
-  bool get persisted() { return _ptr.persisted; }
-
-  void initPageTransitionEvent(String typeArg, bool canBubbleArg, bool cancelableArg, bool persisted) {
-    _ptr.initPageTransitionEvent(typeArg, canBubbleArg, cancelableArg, persisted);
-    return;
-  }
+  bool get persisted() => _ptr.persisted;
 }