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

chromeos/dbus/fake_cras_audio_client.cc

Index: chromeos/dbus/fake_cras_audio_client.cc
diff --git a/chromeos/dbus/fake_cras_audio_client.cc b/chromeos/dbus/fake_cras_audio_client.cc
index 8bffa160f701289d55d84d8b5b8947be240f277c..b8778caab44f9725452715179463c94f0a01309f 100644
--- a/chromeos/dbus/fake_cras_audio_client.cc
+++ b/chromeos/dbus/fake_cras_audio_client.cc
@@ -174,6 +174,11 @@ void FakeCrasAudioClient::AddActiveOutputNode(uint64_t node_id) {
   }
 }
 
+void FakeCrasAudioClient::WaitForServiceToBeAvailable(
+    const WaitForServiceToBeAvailableCallback& callback) {
+  callback.Run(true);
+}
+
 void FakeCrasAudioClient::RemoveActiveOutputNode(uint64_t node_id) {
   for (size_t i = 0; i < node_list_.size(); ++i) {
     if (node_list_[i].id == node_id)