Cleaning up event constructors

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

Index: tools/dom/templates/html/dart2js/impl_MouseEvent.darttemplate
diff --git a/tools/dom/templates/html/dart2js/impl_MouseEvent.darttemplate b/tools/dom/templates/html/dart2js/impl_MouseEvent.darttemplate
index d7e51a7010c13975bcef53cbb3c54f310d273676..ed29b0f3f156c664dde0373a1a03d00d770a65f3 100644
--- a/tools/dom/templates/html/dart2js/impl_MouseEvent.darttemplate
+++ b/tools/dom/templates/html/dart2js/impl_MouseEvent.darttemplate
@@ -5,16 +5,21 @@
 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 {