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

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

 
-class HTMLBodyElementJs extends HTMLElementJs implements HTMLBodyElement native "*HTMLBodyElement" {
+class _HTMLBodyElementJs extends _HTMLElementJs implements HTMLBodyElement native "*HTMLBodyElement" {
 
   String get aLink() native "return this.aLink;";
 
   void set aLink(String value) native "this.aLink = value;";
 
   String get background() native "return this.background;";
 
   void set background(String value) native "this.background = value;";
 
   String get bgColor() native "return this.bgColor;";
 
   void set bgColor(String value) native "this.bgColor = value;";
 
   String get link() native "return this.link;";
 
   void set link(String value) native "this.link = value;";
 
   String get text() native "return this.text;";
 
   void set text(String value) native "this.text = value;";
 
   String get vLink() native "return this.vLink;";
 
   void set vLink(String value) native "this.vLink = value;";
 }