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

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

Index: client/dom/generated/src/frog/MutationRecord.dart
diff --git a/client/dom/generated/src/frog/MutationRecord.dart b/client/dom/generated/src/frog/MutationRecord.dart
index 23eecb89c4fcbca8b4ee2b28632cf4cae47fb852..0c7d48511434a52ebff4f35c40b5dce191df8799 100644
--- a/client/dom/generated/src/frog/MutationRecord.dart
+++ b/client/dom/generated/src/frog/MutationRecord.dart
@@ -1,21 +1,21 @@
 
-class MutationRecordJs extends DOMTypeJs implements MutationRecord native "*MutationRecord" {
+class _MutationRecordJs extends _DOMTypeJs implements MutationRecord native "*MutationRecord" {
 
-  NodeListJs get addedNodes() native "return this.addedNodes;";
+  _NodeListJs get addedNodes() native "return this.addedNodes;";
 
   String get attributeName() native "return this.attributeName;";
 
   String get attributeNamespace() native "return this.attributeNamespace;";
 
-  NodeJs get nextSibling() native "return this.nextSibling;";
+  _NodeJs get nextSibling() native "return this.nextSibling;";
 
   String get oldValue() native "return this.oldValue;";
 
-  NodeJs get previousSibling() native "return this.previousSibling;";
+  _NodeJs get previousSibling() native "return this.previousSibling;";
 
-  NodeListJs get removedNodes() native "return this.removedNodes;";
+  _NodeListJs get removedNodes() native "return this.removedNodes;";
 
-  NodeJs get target() native "return this.target;";
+  _NodeJs get target() native "return this.target;";
 
   String get type() native "return this.type;";
 }