Make dart:dom implementation types private so they don't muddle the docs.

client/dom/generated/src/frog/UIEvent.dart

Index: client/dom/generated/src/frog/UIEvent.dart
diff --git a/client/dom/generated/src/frog/UIEvent.dart b/client/dom/generated/src/frog/UIEvent.dart
index 8b2cae6a41f645bc29ca39bba0a5f45ee3373968..44d4ef1e8687968c7bcb49d37cb27d2932e49237 100644
--- a/client/dom/generated/src/frog/UIEvent.dart
+++ b/client/dom/generated/src/frog/UIEvent.dart
@@ -1,5 +1,5 @@
 
-class UIEventJs extends EventJs implements UIEvent native "*UIEvent" {
+class _UIEventJs extends _EventJs implements UIEvent native "*UIEvent" {
 
   int get charCode() native "return this.charCode;";
 
@@ -15,9 +15,9 @@ class UIEventJs extends EventJs implements UIEvent native "*UIEvent" {
 
   int get pageY() native "return this.pageY;";
 
-  DOMWindowJs get view() native "return this.view;";
+  _DOMWindowJs get view() native "return this.view;";
 
   int get which() native "return this.which;";
 
-  void initUIEvent(String type, bool canBubble, bool cancelable, DOMWindowJs view, int detail) native;
+  void initUIEvent(String type, bool canBubble, bool cancelable, _DOMWindowJs view, int detail) native;
 }