Use deferred loading for message catalogs.

pkg/intl/test/message_extraction/sample_with_messages.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.
 
 /**
  * This is a program with various [Intl.message] messages. It just prints
  * all of them, and is used for testing of message extraction, translation,
  * and code generation.
  */
 library sample;
 
 import "package:intl/intl.dart";
 import "foo_messages_all.dart";
 import "print_to_list.dart";
 import "dart:async";
+import "package:unittest/unittest.dart";
 
 part 'part_of_sample_with_messages.dart';
 
 message1() => Intl.message("This is a message", name: 'message1', desc: 'foo' );
 
 message2(x) => Intl.message("Another message with parameter $x",
     name: 'message2', desc: 'Description 2', args: [x], examples: {'x' : 3});
 
 // A string with multiple adjacent strings concatenated together, verify
 // that the parser handles this properly.
@@ skipping 190 matching lines @@
 }
 
 var localeToUse = 'en_US';
 
 main() {
   var fr = new Intl("fr");
   var english = new Intl("en_US");
   var de = new Intl("de_DE");
   // Throw in an initialize of a null locale to make sure it doesn't throw.
   initializeMessages(null);
-  var f1 = initializeMessages(fr.locale).then((_) => printStuff(fr));
+
+  // Verify that a translated message isn't initially present.
+  var messageInGerman = Intl.withLocale('de_DE', message1);
+  test("Locales don't work before they're initialized", ()
+      => expect(messageInGerman, "This is a message"));
+
+  var f1 = initializeMessages(fr.locale)
+      // Since English has the one message which is always translated, we
+      // can't print it until French is ready.
+      .then((_) => printStuff(english))
+      .then((_) => printStuff(fr));
   var f2 = initializeMessages('de-de').then((_) => printStuff(de));
-  printStuff(english);
   return Future.wait([f1, f2]);
 }