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

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

Index: client/dom/generated/src/frog/HTMLFrameElement.dart
diff --git a/client/dom/generated/src/frog/HTMLFrameElement.dart b/client/dom/generated/src/frog/HTMLFrameElement.dart
index 048049449620cd7708a1c37c3a2dc7f29b429ff5..e36527d6259c723f328b3c161d0d7f88578877e1 100644
--- a/client/dom/generated/src/frog/HTMLFrameElement.dart
+++ b/client/dom/generated/src/frog/HTMLFrameElement.dart
@@ -1,9 +1,9 @@
 
-class HTMLFrameElementJs extends HTMLElementJs implements HTMLFrameElement native "*HTMLFrameElement" {
+class _HTMLFrameElementJs extends _HTMLElementJs implements HTMLFrameElement native "*HTMLFrameElement" {
 
-  DocumentJs get contentDocument() native "return this.contentDocument;";
+  _DocumentJs get contentDocument() native "return this.contentDocument;";
 
-  DOMWindowJs get contentWindow() native "return this.contentWindow;";
+  _DOMWindowJs get contentWindow() native "return this.contentWindow;";
 
   String get frameBorder() native "return this.frameBorder;";
 
@@ -45,5 +45,5 @@ class HTMLFrameElementJs extends HTMLElementJs implements HTMLFrameElement nativ
 
   int get width() native "return this.width;";
 
-  SVGDocumentJs getSVGDocument() native;
+  _SVGDocumentJs getSVGDocument() native;
 }