Cleaning up event constructors

tools/dom/templates/html/impl/impl_CustomEvent.darttemplate

Index: tools/dom/templates/html/impl/impl_CustomEvent.darttemplate
diff --git a/tools/dom/templates/html/impl/impl_CustomEvent.darttemplate b/tools/dom/templates/html/impl/impl_CustomEvent.darttemplate
index b2a7ad46d145adaa01d524fe30246bdb3c6ad1d3..2d2b6c0a8ddc74ea4bd2d4102f47ddc8f46db00f 100644
--- a/tools/dom/templates/html/impl/impl_CustomEvent.darttemplate
+++ b/tools/dom/templates/html/impl/impl_CustomEvent.darttemplate
@@ -7,8 +7,13 @@
 part of html;
 
 $(ANNOTATIONS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
-  factory $CLASSNAME(String type, [bool canBubble = true, bool cancelable = true,
-      Object detail]) => _$(CLASSNAME)FactoryProvider.create$CLASSNAME(
-      type, canBubble, cancelable, detail);
+  factory $CLASSNAME(String type,
+      {bool canBubble: true, bool cancelable: true, Object detail}) {
+
+    final CustomEvent e = document.$dom_createEvent("CustomEvent");
+    e.$dom_initCustomEvent(type, canBubble, cancelable, detail);
+
+    return e;
+  }
 $!MEMBERS
 }