Add constructors to all the event classes.

client/html/src/BeforeLoadEventWrappingImplementation.dart

Index: client/html/src/BeforeLoadEventWrappingImplementation.dart
diff --git a/client/html/generated/src/wrapping/_BeforeLoadEventWrappingImplementation.dart b/client/html/src/BeforeLoadEventWrappingImplementation.dart
similarity index 54%
rename from client/html/generated/src/wrapping/_BeforeLoadEventWrappingImplementation.dart
rename to client/html/src/BeforeLoadEventWrappingImplementation.dart
index 9b59d901e3bfb074236cc91b732c801bccaca449..ec68f301090f48f6d2d365936f5ca837caabbc0d 100644
--- a/client/html/generated/src/wrapping/_BeforeLoadEventWrappingImplementation.dart
+++ b/client/html/src/BeforeLoadEventWrappingImplementation.dart
@@ -2,15 +2,15 @@
 // 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 BeforeLoadEventWrappingImplementation extends EventWrappingImplementation implements BeforeLoadEvent {
-  BeforeLoadEventWrappingImplementation._wrap(ptr) : super._wrap(ptr) {}
-
-  String get url() { return _ptr.url; }
+  BeforeLoadEventWrappingImplementation._wrap(ptr) : super._wrap(ptr);
 
-  void initBeforeLoadEvent(String type, bool canBubble, bool cancelable, String url) {
-    _ptr.initBeforeLoadEvent(type, canBubble, cancelable, url);
-    return;
+  factory BeforeLoadEventWrappingImplementation(String type, String url,
+      [bool canBubble = true, bool cancelable = true]) {
+    final e = dom.document.createEvent("BeforeLoadEvent");
+    e.initBeforeLoadEvent(type, canBubble, cancelable, url);
+    return LevelDom.wrapBeforeLoadEvent(e);
   }
+
+  String get url() => _ptr.url;
 }