Switching AudioInputDeviceManager from using AudioManager interface to AudioSystem one.

media/audio/mock_audio_manager.cc

Index: media/audio/mock_audio_manager.cc
diff --git a/media/audio/mock_audio_manager.cc b/media/audio/mock_audio_manager.cc
index b89cb5e1a8f89179670b8b7126f42e18352ade25..b6c09e0d7077c5826c1dc180c2ae9863ac3f9440 100644
--- a/media/audio/mock_audio_manager.cc
+++ b/media/audio/mock_audio_manager.cc
@@ -115,7 +115,9 @@ AudioParameters MockAudioManager::GetInputStreamParameters(
 std::string MockAudioManager::GetAssociatedOutputDeviceID(
     const std::string& input_device_id) {
   DCHECK(GetTaskRunner()->BelongsToCurrentThread());
-  return std::string();
+  return get_associated_output_device_id_cb_.is_null()
+             ? std::string()
+             : get_associated_output_device_id_cb_.Run(input_device_id);
 }
 
 std::unique_ptr<AudioLog> MockAudioManager::CreateAudioLog(
@@ -167,4 +169,9 @@ void MockAudioManager::SetOutputDeviceDescriptionsCallback(
   get_output_device_descriptions_cb_ = std::move(callback);
 }
 
+void MockAudioManager::SetAssociatedOutputDeviceIDCallback(
+    GetAssociatedOutputDeviceIDCallback callback) {
+  get_associated_output_device_id_cb_ = std::move(callback);
+}
+
 }  // namespace media.