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

ash/system/chromeos/audio/audio_detailed_view.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 "ash/system/chromeos/audio/audio_detailed_view.h"
 
 #include "ash/system/tray/fixed_sized_scroll_view.h"
 #include "ash/system/tray/hover_highlight_view.h"
 #include "ash/system/tray/tray_constants.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 149 matching lines @@
   scroller()->Layout();
 }
 
 void AudioDetailedView::OnViewClicked(views::View* sender) {
   if (sender == footer()->content()) {
     TransitionToDefaultView();
   } else {
     AudioDeviceMap::iterator iter = device_map_.find(sender);
     if (iter == device_map_.end())
       return;
-    chromeos::AudioDevice& device = iter->second;
-    CrasAudioHandler::Get()->SwitchToDevice(device, true);
+    chromeos::AudioDevice device = iter->second;
+    CrasAudioHandler::Get()->SwitchToDevice(device, true,
+                                            CrasAudioHandler::ACTIVATE_BY_USER);
   }
 }
 
 }  // namespace tray
 }  // namespace ash