Patches to support Dart VM patch files in dart2js.

sdk/lib/core/null.dart

Index: sdk/lib/core/null.dart
diff --git a/sdk/lib/core/null.dart b/sdk/lib/core/null.dart
index dd914a3be90ae0ea66c2eabf9c7a0a5263f011af..c046da7818954e4b8f7aefb55c35f9e7a3d08e6c 100644
--- a/sdk/lib/core/null.dart
+++ b/sdk/lib/core/null.dart
@@ -12,10 +12,10 @@ part of dart.core;
  * Null.
  */
 class Null {
-  factory Null._uninstantiable() {
-    throw new UnsupportedError('class Null cannot be instantiated');
-  }
+  external factory Null._uninstantiable();
 
   /** Returns the string `"null"`. */
-  String toString() => "null";
+  external String toString();
+
+  external int get hashCode;
 }