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

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

 
-class HTMLHRElementJs extends HTMLElementJs implements HTMLHRElement native "*HTMLHRElement" {
+class _HTMLHRElementJs extends _HTMLElementJs implements HTMLHRElement native "*HTMLHRElement" {
 
   String get align() native "return this.align;";
 
   void set align(String value) native "this.align = value;";
 
   bool get noShade() native "return this.noShade;";
 
   void set noShade(bool value) native "this.noShade = value;";
 
   String get size() native "return this.size;";
 
   void set size(String value) native "this.size = value;";
 
   String get width() native "return this.width;";
 
   void set width(String value) native "this.width = value;";
 }