Deal with Javascript integer limitations in heap snapshot processing to handle 64-bit target VMs.

runtime/observatory/tests/service/address_mapper_test.dart

+// Copyright (c) 2015, 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.
+// VMOptions=--compile_all --error_on_bad_type --error_on_bad_override
+
+import 'package:observatory/object_graph.dart';
+import 'package:expect/expect.dart';
+
+main() {
+  var map = new AddressMapper(42);
+
+  Expect.equals(null, map.get(1, 2, 3));
+  Expect.equals(4, map.put(1, 2, 3, 4));
+  Expect.equals(4, map.get(1, 2, 3));
+
+  Expect.equals(null, map.get(2, 3, 1));
+  Expect.equals(null, map.get(3, 1, 2));
+
+  Expect.throws(() => map.put(1, 2, 3, 44),
+                (e) => true,
+                "Overwrite key");
+
+  Expect.throws(() => map.put(5, 6, 7, 0),
+                (e) => true,
+                "Invalid value");
+
+  Expect.throws(() => map.put("5", 6, 7, 0),
+                (e) => true,
+                "Invalid key");
+}