Add appengine/gcloud/mustache dependencies.

pkg/appengine/lib/api/memcache.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.
+
+library appengine.api.memcache;
+
+import 'package:gcloud/service_scope.dart' as ss;
+import 'package:memcache/memcache.dart';
+
+/**
+ * Register a new [Memcache] object.
+ *
+ * Calling this outside of a service scope or calling it more than once inside
+ * the same service scope will result in an error.
+ *
+ * See the `package:gcloud/service_scope.dart` library for more information.
+ */
+void registerMemcacheService(Memcache service) {
+  ss.register(#_appengine.memcache, service);
+}
+
+/**
+ * The memcache service.
+ *
+ * Request handlers will be run inside a service scope which contains the
+ * memcache service.
+ */
+Memcache get memcacheService => ss.lookup(#_appengine.memcache);