Add constructors to all the event classes.

client/html/src/DeviceMotionEventWrappingImplementation.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 DeviceMotionEventWrappingImplementation extends EventWrappingImplementation implements DeviceMotionEvent {
+  DeviceMotionEventWrappingImplementation._wrap(ptr) : super._wrap(ptr);
 
-class DeviceMotionEventWrappingImplementation extends EventWrappingImplementation implements DeviceMotionEvent {
-  DeviceMotionEventWrappingImplementation._wrap(ptr) : super._wrap(ptr) {}
+  factory DeviceMotionEventWrappingImplementation(String type,
+      [bool canBubble = true, bool cancelable = true]) {
+    final e = dom.document.createEvent("DeviceMotionEvent");
+    e.initEvent(type, canBubble, cancelable);
+    return LevelDom.wrapDeviceMotionEvent(e);
+  }
 
-  num get interval() { return _ptr.interval; }
+  num get interval() => _ptr.interval;
 }