Add appengine/gcloud/mustache dependencies.

pkg/appengine/lib/src/app_engine_request_handler.dart

Index: pkg/appengine/lib/src/app_engine_request_handler.dart
diff --git a/pkg/appengine/lib/src/app_engine_request_handler.dart b/pkg/appengine/lib/src/app_engine_request_handler.dart
new file mode 100644
index 0000000000000000000000000000000000000000..aacabf42cd2ed96c9bfa6d3e05a5fd597b115975
--- /dev/null
+++ b/pkg/appengine/lib/src/app_engine_request_handler.dart
@@ -0,0 +1,9 @@
+// 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.
+
+library appengine.app_engine_request_handler;
+
+import 'dart:io';
+
+typedef void AppEngineRequestHandler(HttpRequest request);