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

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

Index: client/dom/generated/src/frog/WheelEvent.dart
diff --git a/client/dom/generated/src/frog/WheelEvent.dart b/client/dom/generated/src/frog/WheelEvent.dart
index ae90d30787f81e0cdf03ab6d74a17a0fceb6a6f9..d4bf9e1b0c83b3b63b364fb1f41f0d1c9edaaafc 100644
--- a/client/dom/generated/src/frog/WheelEvent.dart
+++ b/client/dom/generated/src/frog/WheelEvent.dart
@@ -1,5 +1,5 @@
 
-class WheelEventJs extends UIEventJs implements WheelEvent native "*WheelEvent" {
+class _WheelEventJs extends _UIEventJs implements WheelEvent native "*WheelEvent" {
 
   bool get altKey() native "return this.altKey;";
 
@@ -33,5 +33,5 @@ class WheelEventJs extends UIEventJs implements WheelEvent native "*WheelEvent"
 
   int get y() native "return this.y;";
 
-  void initWebKitWheelEvent(int wheelDeltaX, int wheelDeltaY, DOMWindowJs view, int screenX, int screenY, int clientX, int clientY, bool ctrlKey, bool altKey, bool shiftKey, bool metaKey) native;
+  void initWebKitWheelEvent(int wheelDeltaX, int wheelDeltaY, _DOMWindowJs view, int screenX, int screenY, int clientX, int clientY, bool ctrlKey, bool altKey, bool shiftKey, bool metaKey) native;
 }