Add appengine/gcloud/mustache dependencies.

pkg/appengine/lib/src/client_context.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.client_context;
+
+import 'dart:async';
+
+import 'package:gcloud/db.dart';
+import 'package:gcloud/storage.dart';
+import 'package:memcache/memcache.dart';
+
+import '../api/logging.dart';
+import '../api/modules.dart';
+import '../api/remote_api.dart';
+import '../api/users.dart';
+
+abstract class ClientContext {
+  /// Whether the application is currently running in the development
+  /// environment.
+  bool get isDevelopmentEnvironment;
+  /// Whether the application is currently running in the production
+  /// environment.
+  bool get isProductionEnvironment;
+
+  Services get services;
+  Assets get assets;
+}
+
+abstract class Services {
+  DatastoreDB get db;
+
+  /// Access the gcloud package storage API. This will autumatically be
+  /// available on deployed App Engine applications. For local testing this
+  /// will be `null` unless the environemnt variable
+  /// `STORAGE_SERVICE_ACCOUNT_FILE` is passed in `app.yaml`. This environment
+  /// variable should point to a private key for a service account in JSON
+  /// format.
+  Storage get storage;
+  Logging get logging;
+  Memcache get memcache;
+  ModulesService get modules;
+  RemoteApi get remoteApi;
+  UserService get users;
+}
+
+class AssetError implements Exception {
+  final String message;
+
+  AssetError(this.message);
+
+  String toString() => "AssetError: $message";
+}
+
+abstract class Assets {
+  /**
+   * Read an asset. If [path] is not specified the path
+   * from the active request is used.
+   */
+  Future<Stream<List<int>>> read([String path]);
+
+  /**
+   * Serve a asset to the active response. If [path]
+   * is not specified the path from the active request is used.
+   */
+  void serve([String path]);
+}