Move toString() to collection classes.

tests/corelib/list_to_string2_test.dart

+// 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";
+
+main() {
+  List list = [1, 2];
+  list.add(list);
+
+  List list2 = new List(4);
+  list2[0] = 1;
+  list2[1] = 2;
+  list2[2] = list2;
+  list2[3] = list;
+
+  Expect.equals("[1, 2, [...]]", list.toString());
+  Expect.equals("[1, 2, [...], [1, 2, [...]]]", list2.toString());
+
+  // Throwing in the middle of a toString does not leave the
+  // list as being visited.
+  List list3 = [1, 2, new ThrowOnToString(), 4];
+  Expect.throws(list3.toString, (e) => e == "Bad!");
+  list3[2] = 3;
+  Expect.equals("[1, 2, 3, 4]", list3.toString());
+}
+
+class ThrowOnToString {
+
+  String toString() {
+    throw "Bad!";
+  }
+}