Merging dart:html interfaces and implementations

sdk/lib/html/templates/html/dart2js/impl_MouseEvent.darttemplate

Index: sdk/lib/html/templates/html/dart2js/impl_MouseEvent.darttemplate
diff --git a/sdk/lib/html/templates/html/dart2js/impl_MouseEvent.darttemplate b/sdk/lib/html/templates/html/dart2js/impl_MouseEvent.darttemplate
index 62aaa4e72419ce421b5c2c7c102736b1f2caa14b..cda9bda4f85d886879b587779b88a8421f839d20 100644
--- a/sdk/lib/html/templates/html/dart2js/impl_MouseEvent.darttemplate
+++ b/sdk/lib/html/templates/html/dart2js/impl_MouseEvent.darttemplate
@@ -3,6 +3,16 @@
 // BSD-style license that can be found in the LICENSE file.
 
 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);
 $!MEMBERS
 
   int get offsetX {