A few API changes:

tools/dom/src/native_DOMImplementation.dart

Index: tools/dom/src/native_DOMImplementation.dart
diff --git a/tools/dom/src/native_DOMImplementation.dart b/tools/dom/src/native_DOMImplementation.dart
index cbea9eda1b4dc69f198b662d1de38e16057cb770..e650c6fd0c5c0aef41f0256b35e434d6420ea27e 100644
--- a/tools/dom/src/native_DOMImplementation.dart
+++ b/tools/dom/src/native_DOMImplementation.dart
@@ -87,6 +87,8 @@ class _Utils {
 
   static bool isMap(obj) => obj is Map;
 
+  static List toListIfIterable(obj) => obj is Iterable ? obj.toList() : null;
+
   static Map createMap() => {};
 
   static makeUnimplementedError(String fileName, int lineNo) {
@@ -393,10 +395,6 @@ class _Utils {
 
   static bool isNoSuchMethodError(obj) => obj is NoSuchMethodError;
 
-  // TODO(jacobr): we need a failsafe way to determine that a Node is really a
-  // DOM node rather than just a class that extends Node.
-  static bool isNode(obj) => obj is Node;
-
   static bool _isBuiltinType(ClassMirror cls) {
     // TODO(vsm): Find a less hackish way to do this.
     LibraryMirror lib = cls.owner;