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

client/html/generated/html/frog/InputElement.dart

Index: client/html/generated/html/frog/InputElement.dart
diff --git a/client/html/generated/html/frog/InputElement.dart b/client/html/generated/html/frog/InputElement.dart
index 156ebe6324a08d5c3c933b7abd1147bf65b57eba..a8d053798110681614535895ff50c6a005aba33d 100644
--- a/client/html/generated/html/frog/InputElement.dart
+++ b/client/html/generated/html/frog/InputElement.dart
@@ -1,6 +1,9 @@
 
 class _InputElementImpl extends _ElementImpl implements InputElement native "*HTMLInputElement" {
 
+  _InputElementEventsImpl get on() =>
+    new _InputElementEventsImpl(this);
+
   String accept;
 
   String align;
@@ -91,9 +94,6 @@ class _InputElementImpl extends _ElementImpl implements InputElement native "*HT
 
   final bool willValidate;
 
-  _InputElementEventsImpl get on() =>
-    new _InputElementEventsImpl(this);
-
   bool checkValidity() native;
 
   void select() native;