Use unordered map hash on ConstructedConstantValue.

tests/compiler/dart2js/constant_value_test.dart

+// Copyright (c) 2016, 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.
+
+library dart2js.constants.values.test;
+
+import 'package:async_helper/async_helper.dart';
+import 'package:expect/expect.dart';
+import 'package:compiler/src/helpers/helpers.dart';
+import 'package:compiler/src/elements/elements.dart';
+import 'package:compiler/src/constants/values.dart';
+import 'type_test_helper.dart';
+
+void main() {
+  enableDebugMode();
+
+  asyncTest(() async {
+    TypeEnvironment env = await TypeEnvironment.create('''
+    class C {
+      final field1;
+      final field2;
+
+      C(this.field1, this.field2);
+    }
+    ''');
+    ClassElement C = env.getElement('C');
+    FieldElement field1 = C.lookupLocalMember('field1');
+    FieldElement field2 = C.lookupLocalMember('field2');
+    ConstantValue value1 = new ConstructedConstantValue(C.rawType, {
+      field1: new IntConstantValue(0),
+      field2: new IntConstantValue(1),
+    });
+    ConstantValue value2 = new ConstructedConstantValue(C.rawType, {
+      field2: new IntConstantValue(1),
+      field1: new IntConstantValue(0),
+    });
+    Expect.equals(value1.hashCode, value2.hashCode, "Hashcode mismatch.");
+    Expect.equals(value1, value2, "Value mismatch.");
+  });
+}