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

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

 
-class TreeWalkerJs extends DOMTypeJs implements TreeWalker native "*TreeWalker" {
+class _TreeWalkerJs extends _DOMTypeJs implements TreeWalker native "*TreeWalker" {
 
-  NodeJs get currentNode() native "return this.currentNode;";
+  _NodeJs get currentNode() native "return this.currentNode;";
 
-  void set currentNode(NodeJs value) native "this.currentNode = value;";
+  void set currentNode(_NodeJs value) native "this.currentNode = value;";
 
   bool get expandEntityReferences() native "return this.expandEntityReferences;";
 
-  NodeFilterJs get filter() native "return this.filter;";
+  _NodeFilterJs get filter() native "return this.filter;";
 
-  NodeJs get root() native "return this.root;";
+  _NodeJs get root() native "return this.root;";
 
   int get whatToShow() native "return this.whatToShow;";
 
-  NodeJs firstChild() native;
+  _NodeJs firstChild() native;
 
-  NodeJs lastChild() native;
+  _NodeJs lastChild() native;
 
-  NodeJs nextNode() native;
+  _NodeJs nextNode() native;
 
-  NodeJs nextSibling() native;
+  _NodeJs nextSibling() native;
 
-  NodeJs parentNode() native;
+  _NodeJs parentNode() native;
 
-  NodeJs previousNode() native;
+  _NodeJs previousNode() native;
 
-  NodeJs previousSibling() native;
+  _NodeJs previousSibling() native;
 }