Cleaning up event constructors

tools/dom/templates/html/dart2js/impl_MouseEvent.darttemplate

 // Copyright (c) 2012, 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.
 
 part of html;
 
 $(ANNOTATIONS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
-  factory $CLASSNAME(String type, Window view, int detail, int screenX,
-      int screenY, int clientX, int clientY, int button, [bool canBubble = true,
-      bool cancelable = true, bool ctrlKey = false, bool altKey = false,
-      bool shiftKey = false, bool metaKey = false,
-      EventTarget relatedTarget = null]) =>
-      _$(CLASSNAME)FactoryProvider.create$CLASSNAME(
-          type, view, detail, screenX, screenY,
-          clientX, clientY, button, canBubble, cancelable,
-          ctrlKey, altKey, shiftKey, metaKey,
-          relatedTarget);
+  factory $CLASSNAME(String type,
+      {Window view, int detail: 0, int screenX: 0, int screenY: 0,
+      int clientX: 0, int clientY: 0, int button: 0, bool canBubble: true,
+      bool cancelable: true, bool ctrlKey: false, bool altKey: false,
+      bool shiftKey: false, bool metaKey: false, EventTarget relatedTarget}) {
+
+    if (view == null) {
+      view = window;
+    }
+    var event = document.$dom_createEvent('MouseEvent');
+    event.$dom_initMouseEvent(type, canBubble, cancelable, view, detail,
+        screenX, screenY, clientX, clientY, ctrlKey, altKey, shiftKey, metaKey,
+        button, relatedTarget);
+    return event;
+  }
 $!MEMBERS
 
   int get offsetX {
   if (JS('bool', '!!#.offsetX', this)) {
       return JS('int', '#.offsetX', this);
     } else {
       // Firefox does not support offsetX.
       var target = this.target;
       if (!(target is Element)) {
         throw new UnsupportedError(
@@ skipping 10 matching lines @@
       // Firefox does not support offsetY.
       var target = this.target;
       if (!(target is Element)) {
         throw new UnsupportedError(
             'offsetY is only supported on elements');
       }
       return this.clientY - this.target.getBoundingClientRect().top;
     }
   }
 }