Persist the user's active audio device choice across chromeos session and reboots.

chromeos/dbus/cras_audio_client.h

 // Copyright (c) 2013 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.
 
 #ifndef CHROMEOS_DBUS_CRAS_AUDIO_CLIENT_H_
 #define CHROMEOS_DBUS_CRAS_AUDIO_CLIENT_H_
 
 #include <stdint.h>
 
 #include "base/callback.h"
@@ skipping 52 matching lines @@
   // GetNodesCallback is used for GetNodes method. It receives 2 arguments,
   // |audio_nodes| which containing a list of audio nodes data and
   // |success| which indicates whether or not the request succeeded.
   typedef base::Callback<void(const AudioNodeList&, bool)> GetNodesCallback;
 
   // ErrorCallback is used for cras dbus method error response. It receives 2
   // arguments, |error_name| indicates the dbus error name, and |error_message|
   // contains the detailed dbus error message.
   typedef base::Callback<void(const std::string&,
                               const std::string&)> ErrorCallback;
+  // A callback for cras dbus method WaitForServiceToBeAvailable.
+  typedef base::Callback<void(bool service_is_ready)>
+      WaitForServiceToBeAvailableCallback;
 
   // Gets the volume state, asynchronously.
   virtual void GetVolumeState(const GetVolumeStateCallback& callback) = 0;
 
   // Gets an array of audio input and output nodes.
   virtual void GetNodes(const GetNodesCallback& callback,
                         const ErrorCallback& error_callback) = 0;
 
   // Sets output volume of the given |node_id| to |volume|, in the rage of
   // [0, 100].
@@ skipping 35 matching lines @@
   // removing an active output node added by AddActiveOutputNode.
   virtual void RemoveActiveOutputNode(uint64_t node_id) = 0;
 
   // Swaps the left and right channel of the primary active output device.
   // Swap the left and right channel if |swap| is true; otherwise, swap the left
   // and right channel back to the normal mode.
   // The dbus message will be dropped if this feature is not supported on the
   // |node_id|.
   virtual void SwapLeftRight(uint64_t node_id, bool swap) = 0;
 
+  // Runs the callback as soon as the service becomes available.
+  virtual void WaitForServiceToBeAvailable(
+      const WaitForServiceToBeAvailableCallback& callback) = 0;
+
   // Creates the instance.
   static CrasAudioClient* Create();
 
  protected:
   // Create() should be used instead.
   CrasAudioClient();
 
  private:
   DISALLOW_COPY_AND_ASSIGN(CrasAudioClient);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_DBUS_CRAS_AUDIO_CLIENT_H_