app_shell: Initial skeleton of a GCD target device setup API

extensions/shell/common/api/shell_gcd.idl

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Setup related functions for a Google Cloud Devices (GCD) target device
+// running on Chrome OS Core. The actual bootstrapping and GCD registration is
+// handled by the privetd and buffet system daemons.
+namespace shell.gcd {
+  
+  enum SetupStatus {
+    // Not yet configured. Waiting for a connection from the phone or laptop
+    // setup app.
+    unconfigured,
+
+    // Displaying code for user to verify they wish to set up this device.
+    confirmingSetup,
+    
+    // Establishing a secure connection to the setup device and exchanging the
+    // Wi-Fi credentials. 
+    exchangingCredentials,
+    
+    // Connecting to the local network.
+    connectingToNetwork,
+    
+    // Registering with the GCD backend.
+    registering,
+    
+    // Setup completed.
+    completed
+  };
+  
+  callback SetupStatusCallback = void(SetupStatus status);
+
+  interface Functions {
+    // Returns the current setup status via |callback|.
+    static void getSetupStatus(SetupStatusCallback callback);
+  };
+  
+  interface Events {
+    // Notifies that setup has transitioned to a new |status|.
+    static void onSetupStatusChanged(SetupStatus status);
+  };
+};