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

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

Index: client/dom/generated/src/frog/Touch.dart
diff --git a/client/dom/generated/src/frog/Touch.dart b/client/dom/generated/src/frog/Touch.dart
index de1770f34a0daa01d794e792073194543595c887..31aacdc5688e39390191caedddebc5ac11df1b3e 100644
--- a/client/dom/generated/src/frog/Touch.dart
+++ b/client/dom/generated/src/frog/Touch.dart
@@ -1,5 +1,5 @@
 
-class TouchJs extends DOMTypeJs implements Touch native "*Touch" {
+class _TouchJs extends _DOMTypeJs implements Touch native "*Touch" {
 
   int get clientX() native "return this.clientX;";
 
@@ -15,7 +15,7 @@ class TouchJs extends DOMTypeJs implements Touch native "*Touch" {
 
   int get screenY() native "return this.screenY;";
 
-  EventTargetJs get target() native "return this.target;";
+  _EventTargetJs get target() native "return this.target;";
 
   num get webkitForce() native "return this.webkitForce;";