Refactor the event-generation code to locate it in systemhtml.py.

client/html/generated/html/frog/SVGElementInstance.dart

Index: client/html/generated/html/frog/SVGElementInstance.dart
diff --git a/client/html/generated/html/frog/SVGElementInstance.dart b/client/html/generated/html/frog/SVGElementInstance.dart
index fe10a5fbd52148f6d97c72b2ece025a0017fc6a3..5e7912cd14cf57dedcf06f0192aa439f8ca40119 100644
--- a/client/html/generated/html/frog/SVGElementInstance.dart
+++ b/client/html/generated/html/frog/SVGElementInstance.dart
@@ -1,6 +1,9 @@
 
 class _SVGElementInstanceImpl extends _EventTargetImpl implements SVGElementInstance native "*SVGElementInstance" {
 
+  _SVGElementInstanceEventsImpl get on() =>
+    new _SVGElementInstanceEventsImpl(this);
+
   final _SVGElementInstanceListImpl childNodes;
 
   final _SVGElementImpl correspondingElement;
@@ -17,9 +20,6 @@ class _SVGElementInstanceImpl extends _EventTargetImpl implements SVGElementInst
 
   final _SVGElementInstanceImpl previousSibling;
 
-  _SVGElementInstanceEventsImpl get on() =>
-    new _SVGElementInstanceEventsImpl(this);
-
   void _addEventListener(String type, EventListener listener, [bool useCapture = null]) native "this.addEventListener(type, listener, useCapture);";
 
   bool _dispatchEvent(_EventImpl event) native "return this.dispatchEvent(event);";