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

chromeos/audio/cras_audio_handler.cc

Index: chromeos/audio/cras_audio_handler.cc
diff --git a/chromeos/audio/cras_audio_handler.cc b/chromeos/audio/cras_audio_handler.cc
index cb3e47ea1cf9a12fa3339c05a54435af26ed1ee3..d08d237578e51c6ef962e401775e63f28bec09fc 100644
--- a/chromeos/audio/cras_audio_handler.cc
+++ b/chromeos/audio/cras_audio_handler.cc
@@ -831,15 +831,28 @@ void CrasAudioHandler::UpdateDevicesAndSwitchActive(
   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);
+    }
   }
 }