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

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

 
-class TextTrackCueJs extends DOMTypeJs implements TextTrackCue native "*TextTrackCue" {
+class _TextTrackCueJs extends _DOMTypeJs implements TextTrackCue native "*TextTrackCue" {
 
   String get alignment() native "return this.alignment;";
 
   void set alignment(String value) native "this.alignment = value;";
 
   String get direction() native "return this.direction;";
 
   void set direction(String value) native "this.direction = value;";
 
   num get endTime() native "return this.endTime;";
@@ skipping 33 matching lines @@
   void set startTime(num value) native "this.startTime = value;";
 
   String get text() native "return this.text;";
 
   void set text(String value) native "this.text = value;";
 
   int get textPosition() native "return this.textPosition;";
 
   void set textPosition(int value) native "this.textPosition = value;";
 
-  TextTrackJs get track() native "return this.track;";
+  _TextTrackJs get track() native "return this.track;";
 
   void addEventListener(String type, EventListener listener, [bool useCapture = null]) native;
 
-  bool dispatchEvent(EventJs evt) native;
+  bool dispatchEvent(_EventJs evt) native;
 
-  DocumentFragmentJs getCueAsHTML() native;
+  _DocumentFragmentJs getCueAsHTML() native;
 
   void removeEventListener(String type, EventListener listener, [bool useCapture = null]) native;
 }