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

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

Index: client/dom/generated/src/frog/HTMLLinkElement.dart
diff --git a/client/dom/generated/src/frog/HTMLLinkElement.dart b/client/dom/generated/src/frog/HTMLLinkElement.dart
index b3fef22197a87c9d34976e03b8239ebf58cc13ec..64427acf66c5b4525cf0b81d95d08924d98ce3e0 100644
--- a/client/dom/generated/src/frog/HTMLLinkElement.dart
+++ b/client/dom/generated/src/frog/HTMLLinkElement.dart
@@ -1,5 +1,5 @@
 
-class HTMLLinkElementJs extends HTMLElementJs implements HTMLLinkElement native "*HTMLLinkElement" {
+class _HTMLLinkElementJs extends _HTMLElementJs implements HTMLLinkElement native "*HTMLLinkElement" {
 
   String get charset() native "return this.charset;";
 
@@ -29,11 +29,11 @@ class HTMLLinkElementJs extends HTMLElementJs implements HTMLLinkElement native
 
   void set rev(String value) native "this.rev = value;";
 
-  StyleSheetJs get sheet() native "return this.sheet;";
+  _StyleSheetJs get sheet() native "return this.sheet;";
 
-  DOMSettableTokenListJs get sizes() native "return this.sizes;";
+  _DOMSettableTokenListJs get sizes() native "return this.sizes;";
 
-  void set sizes(DOMSettableTokenListJs value) native "this.sizes = value;";
+  void set sizes(_DOMSettableTokenListJs value) native "this.sizes = value;";
 
   String get target() native "return this.target;";