Re-arrange tests to allow testing generated messages code in dart2js

pkg/intl/test/message_extraction/foo_messages_all.dart

+/**
+ * DO NOT EDIT. This is code generated via pkg/intl/generate_localized.dart
+ * This is a library that looks up messages for specific locales by
+ * delegating to the appropriate library.
+ */
+
+library messages_all;
+
+import 'dart:async';
+import 'package:intl/message_lookup_by_library.dart';
+import 'package:intl/src/intl_helpers.dart';
+import 'package:intl/intl.dart';
+
+import 'foo_messages_fr.dart' as fr;
+import 'foo_messages_de_DE.dart' as de_DE;
+
+
+MessageLookupByLibrary _findExact(localeName) {
+  switch (localeName) {
+    case 'fr' : return fr.messages;
+    case 'de_DE' : return de_DE.messages;
+    default: return null;
+  }
+}
+
+/** User programs should call this before using [localeName] for messages.*/
+Future initializeMessages(String localeName) {
+  initializeInternalMessageLookup(() => new CompositeMessageLookup());
+  messageLookup.addLocale(localeName, _findGeneratedMessagesFor);
+  // TODO(alanknight): Restore once Issue 12824 is fixed.
+  // var lib = deferredLibraries[localeName];
+  // return lib == null ? new Future.value(false) : lib.load();
+  return new Future.value(true);
+}
+
+MessageLookupByLibrary _findGeneratedMessagesFor(locale) {
+  var actualLocale = Intl.verifiedLocale(locale, (x) => _findExact(x) != null);
+  if (actualLocale == null) return null;
+  return _findExact(actualLocale);
+}