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

extensions/shell/browser/shell_audio_controller_chromeos.cc

 // 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.
 
 #include "extensions/shell/browser/shell_audio_controller_chromeos.h"
 
 #include <algorithm>
 
 #include "chromeos/audio/audio_device.h"
 
@@ skipping 60 matching lines @@
     if (it->is_input && !best_input)
       best_input = it->id;
     else if (!it->is_input && !best_output)
       best_output = it->id;
   }
 
   if (best_input && best_input != handler->GetPrimaryActiveInputNode()) {
     const chromeos::AudioDevice* device = GetDevice(devices, best_input);
     DCHECK(device);
     VLOG(1) << "Activating input device: " << device->ToString();
-    handler->SwitchToDevice(*device, true);
+    handler->SwitchToDevice(*device, true,
+                            chromeos::CrasAudioHandler::ACTIVATE_BY_USER);
   }
   if (best_output && best_output != handler->GetPrimaryActiveOutputNode()) {
     const chromeos::AudioDevice* device = GetDevice(devices, best_output);
     DCHECK(device);
     VLOG(1) << "Activating output device: " << device->ToString();
-    handler->SwitchToDevice(*device, true);
+    handler->SwitchToDevice(*device, true,
+                            chromeos::CrasAudioHandler::ACTIVATE_BY_USER);
   }
 }
 
 }  // namespace extensions