Add corelib tests

test/codegen/corelib/map_to_string_test.dart

Index: test/codegen/corelib/map_to_string_test.dart
diff --git a/test/codegen/corelib/map_to_string_test.dart b/test/codegen/corelib/map_to_string_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..8d2bc9b8e40768577d3bd9938d8de92ce10a58ab
--- /dev/null
+++ b/test/codegen/corelib/map_to_string_test.dart
@@ -0,0 +1,33 @@
+// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import "package:expect/expect.dart";
+
+void main() {
+  Map m = new Map();
+
+  m[0] = 0;
+  m[1] = 1;
+  m[2] = m;
+
+  Expect.equals('{0: 0, 1: 1, 2: {...}}', m.toString());
+
+  // Throwing in the middle of a toString does not leave the
+  // map as being visited
+  ThrowOnToString err = new ThrowOnToString();
+  m[1] = err;
+  Expect.throws(m.toString, (e) => e == "Bad!");
+  m[1] = 1;
+  Expect.equals('{0: 0, 1: 1, 2: {...}}', m.toString());
+  m[err] = 1;
+  Expect.throws(m.toString, (e) => e == "Bad!");
+  m.remove(err);
+}
+
+class ThrowOnToString {
+
+  String toString() {
+    throw "Bad!";
+  }
+}