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

chromeos/audio/cras_audio_handler_unittest.cc

Index: chromeos/audio/cras_audio_handler_unittest.cc
diff --git a/chromeos/audio/cras_audio_handler_unittest.cc b/chromeos/audio/cras_audio_handler_unittest.cc
index ea0b6a7467ba7bc712925314ed502c616d9549d5..1e9a2f725b503ba2e1c6a7abc5b84b13053cb1aa 100644
--- a/chromeos/audio/cras_audio_handler_unittest.cc
+++ b/chromeos/audio/cras_audio_handler_unittest.cc
@@ -218,7 +218,7 @@ class TestObserver : public chromeos::CrasAudioHandler::AudioObserver {
   }
 
   void reset_active_input_node_changed_count() {
-    active_output_node_changed_count_ = 0;
+    active_input_node_changed_count_ = 0;
   }
 
   int audio_nodes_changed_count() const {
@@ -2284,4 +2284,28 @@ TEST_F(CrasAudioHandlerTest,
             cras_audio_handler_->GetPrimaryActiveInputNode());
 }
 
+TEST_F(CrasAudioHandlerTest, NoMoreAudioInputDevices) {
+  // Some device like chromebox does not have the internal input device. The
+  // active devices should be reset when the user plugs a device and then
+  // unplugs it to such device.
+
+  AudioNodeList audio_nodes;
+  audio_nodes.push_back(kInternalSpeaker);
+  SetUpCrasAudioHandler(audio_nodes);
+
+  EXPECT_EQ(0ULL, cras_audio_handler_->GetPrimaryActiveInputNode());
+
+  audio_nodes.push_back(kMicJack);
+  ChangeAudioNodes(audio_nodes);
+
+  EXPECT_EQ(kMicJack.id, cras_audio_handler_->GetPrimaryActiveInputNode());
+  EXPECT_EQ(1, test_observer_->active_input_node_changed_count());
+  test_observer_->reset_active_input_node_changed_count();
+
+  audio_nodes.pop_back();
+  ChangeAudioNodes(audio_nodes);
+  EXPECT_EQ(0ULL, cras_audio_handler_->GetPrimaryActiveInputNode());
+  EXPECT_EQ(1, test_observer_->active_input_node_changed_count());
+}
+
 }  // namespace chromeos