Don't put private members in dart:html interfaces.

client/dom/templates/html/impl/impl_Node.darttemplate

Index: client/dom/templates/html/impl/impl_Node.darttemplate
diff --git a/client/dom/templates/html/impl/impl_Node.darttemplate b/client/dom/templates/html/impl/impl_Node.darttemplate
index 531b64bc24460e75cd8dded64a89663457950408..6e0becf7c152249bba2da3ce1bb4ebf4e662e6ad 100644
--- a/client/dom/templates/html/impl/impl_Node.darttemplate
+++ b/client/dom/templates/html/impl/impl_Node.darttemplate
@@ -22,14 +22,16 @@ class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
   // TODO(jacobr): should we throw an exception if parent is already null?
   _NodeImpl remove() {
     if (this.parent != null) {
-      this.parent._removeChild(this);
+      final _NodeImpl parent = this.parent;
+      parent._removeChild(this);
     }
     return this;
   }
 
   _NodeImpl replaceWith(Node otherNode) {
     try {
-      this.parent._replaceChild(otherNode, this);
+      final _NodeImpl parent = this.parent;
+      parent._replaceChild(otherNode, this);
     } catch(var e) {
       
     };