Add constructors to all the event classes.

client/html/src/CustomEventWrappingImplementation.dart

Index: client/html/src/CustomEventWrappingImplementation.dart
diff --git a/client/html/generated/src/wrapping/_CustomEventWrappingImplementation.dart b/client/html/src/CustomEventWrappingImplementation.dart
similarity index 54%
rename from client/html/generated/src/wrapping/_CustomEventWrappingImplementation.dart
rename to client/html/src/CustomEventWrappingImplementation.dart
index c08e8a23c1a9ebcf9338b9a0f742ff4d536b6fec..cace95697d631286ca077ce05d006872a2a54958 100644
--- a/client/html/generated/src/wrapping/_CustomEventWrappingImplementation.dart
+++ b/client/html/src/CustomEventWrappingImplementation.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 CustomEventWrappingImplementation extends EventWrappingImplementation implements CustomEvent {
-  CustomEventWrappingImplementation._wrap(ptr) : super._wrap(ptr) {}
-
-  String get detail() { return _ptr.detail; }
+  CustomEventWrappingImplementation._wrap(ptr) : super._wrap(ptr);
 
-  void initCustomEvent(String typeArg, bool canBubbleArg, bool cancelableArg, Object detailArg) {
-    _ptr.initCustomEvent(typeArg, canBubbleArg, cancelableArg, LevelDom.unwrapMaybePrimitive(detailArg));
-    return;
+  factory CustomEventWrappingImplementation(String type,
+      [bool canBubble = true, bool cancelable = true, Object detail = null]) {
+    final e = dom.document.createEvent("CustomEvent");
+    e.initCustomEvent(type, canBubble, cancelable, detail);
+    return LevelDom.wrapCustomEvent(e);
   }
+
+  String get detail() => _ptr.detail;
 }