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

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

 
-class HTMLAnchorElementJs extends HTMLElementJs implements HTMLAnchorElement native "*HTMLAnchorElement" {
+class _HTMLAnchorElementJs extends _HTMLElementJs implements HTMLAnchorElement native "*HTMLAnchorElement" {
 
   String get charset() native "return this.charset;";
 
   void set charset(String value) native "this.charset = value;";
 
   String get coords() native "return this.coords;";
 
   void set coords(String value) native "this.coords = value;";
 
   String get download() native "return this.download;";
@@ skipping 63 matching lines @@
   void set target(String value) native "this.target = value;";
 
   String get text() native "return this.text;";
 
   String get type() native "return this.type;";
 
   void set type(String value) native "this.type = value;";
 
   String toString() native;
 }