Load deferred chunks in the right order.

tests/compiler/dart2js_extra/deferred/deferred_overlapping_test.dart

+// Copyright (c) 2014, 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 "deferred_overlapping_lib1.dart" deferred as lib1;
+import "deferred_overlapping_lib2.dart" deferred as lib2;
+
+// lib1.C1 and lib2.C2 has a shared base class It will go in its own hunk.
+// If lib1 or lib2s hunks are loaded before the common hunk, the program
+// will fail because the base class does not exist.
+void main() {
+  lib1.loadLibrary().then((_) {
+    var a = new lib1.C1();
+    lib2.loadLibrary().then((_) {
+      var b = new lib2.C2();
+    });
+  });
+}