Add min and max to Iterable and Stream.

runtime/lib/array.dart

Index: runtime/lib/array.dart
diff --git a/runtime/lib/array.dart b/runtime/lib/array.dart
index fd42a675c083112662266f788f4504518d1b411d..4fa5b145f464bdb262d6ec1aa9a516429a4f9a04 100644
--- a/runtime/lib/array.dart
+++ b/runtime/lib/array.dart
@@ -192,6 +192,10 @@ class _ObjectArray<E> implements List<E> {
     throw new StateError("More than one element");
   }
 
+  E min([int compare(E a, E b)]) => Collections.min(this, compare);
+
+  E max([int compare(E a, E b)]) => Collections.max(this, compare);
+
   List<E> toList() {
     return new List<E>.from(this);
   }