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

ash/system/chromeos/audio/audio_detailed_view.cc

Index: ash/system/chromeos/audio/audio_detailed_view.cc
diff --git a/ash/system/chromeos/audio/audio_detailed_view.cc b/ash/system/chromeos/audio/audio_detailed_view.cc
index 2e769434773f2a65b11d9689f6b9f3361ec4215b..ec960ee229758118eaeea9949eef97bc3b4e6f06 100644
--- a/ash/system/chromeos/audio/audio_detailed_view.cc
+++ b/ash/system/chromeos/audio/audio_detailed_view.cc
@@ -167,8 +167,9 @@ void AudioDetailedView::OnViewClicked(views::View* sender) {
     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);
   }
 }