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

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

Index: client/dom/generated/src/frog/DOMImplementation.dart
diff --git a/client/dom/generated/src/frog/DOMImplementation.dart b/client/dom/generated/src/frog/DOMImplementation.dart
index d0236bfe8c8531774f72fd09d996e16a68bfdd69..e16a893e653199648a0c179ca047964359eac66a 100644
--- a/client/dom/generated/src/frog/DOMImplementation.dart
+++ b/client/dom/generated/src/frog/DOMImplementation.dart
@@ -1,13 +1,13 @@
 
-class DOMImplementationJs extends DOMTypeJs implements DOMImplementation native "*DOMImplementation" {
+class _DOMImplementationJs extends _DOMTypeJs implements DOMImplementation native "*DOMImplementation" {
 
-  CSSStyleSheetJs createCSSStyleSheet(String title, String media) native;
+  _CSSStyleSheetJs createCSSStyleSheet(String title, String media) native;
 
-  DocumentJs createDocument(String namespaceURI, String qualifiedName, DocumentTypeJs doctype) native;
+  _DocumentJs createDocument(String namespaceURI, String qualifiedName, _DocumentTypeJs doctype) native;
 
-  DocumentTypeJs createDocumentType(String qualifiedName, String publicId, String systemId) native;
+  _DocumentTypeJs createDocumentType(String qualifiedName, String publicId, String systemId) native;
 
-  HTMLDocumentJs createHTMLDocument(String title) native;
+  _HTMLDocumentJs createHTMLDocument(String title) native;
 
   bool hasFeature(String feature, String version) native;
 }