Reset the active audio node id once all of the devices are gone.

chromeos/audio/cras_audio_handler.cc

 // 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.
 
 #include "chromeos/audio/cras_audio_handler.h"
 
 #include <algorithm>
 #include <cmath>
 
 #include "base/bind.h"
@@ skipping 813 matching lines @@
     else
       output_devices_pq_.push(device);
   }
 
   // If audio nodes change is caused by unplugging some non-active audio
   // devices, the previously set active audio device will stay active.
   // Otherwise, switch to a new active audio device according to their priority.
   if (input_devices_changed &&
       !NonActiveDeviceUnplugged(old_audio_devices_size,
                                 audio_devices_.size(),
-                                active_input_node_id_) &&
-      !input_devices_pq_.empty())
-    SwitchToDevice(input_devices_pq_.top(), true);
+                                active_input_node_id_)) {
+    // Some devices like chromeboxes don't have the internal audio input. In
+    // that case the active input node id should be reset.
+    if (input_devices_pq_.empty()) {
+      active_input_node_id_ = 0;
+      NotifyActiveNodeChanged(true);
+    } else {
+      SwitchToDevice(input_devices_pq_.top(), true);
+    }
+  }
   if (output_devices_changed &&
       !NonActiveDeviceUnplugged(old_audio_devices_size,
                                 audio_devices_.size(),
-                                active_output_node_id_) &&
-      !output_devices_pq_.empty()) {
-    SwitchToDevice(output_devices_pq_.top(), true);
+                                active_output_node_id_)) {
+    // This is really unlikely to happen because all ChromeOS devices have the
+    // internal audio output.
+    if (output_devices_pq_.empty()) {
+      active_output_node_id_ = 0;
+      NotifyActiveNodeChanged(false);
+    } else {
+      SwitchToDevice(output_devices_pq_.top(), true);
+    }
   }
 }
 
 void CrasAudioHandler::HandleGetNodes(const chromeos::AudioNodeList& node_list,
                                       bool success) {
   if (!success) {
     LOG_IF(ERROR, log_errors_) << "Failed to retrieve audio nodes data";
     return;
   }
 
@@ skipping 57 matching lines @@
       active_output_node_id_ = 0;
     chromeos::DBusThreadManager::Get()
         ->GetCrasAudioClient()
         ->RemoveActiveOutputNode(node_id);
     if (notify)
       NotifyActiveNodeChanged(false);
   }
 }
 
 }  // namespace chromeos