Implement MojoAudioRendererSink and use it in UtilityMojoMediaClient

media/mojo/services/media_service_unittest.cc

Index: media/mojo/services/media_service_unittest.cc
diff --git a/media/mojo/services/media_service_unittest.cc b/media/mojo/services/media_service_unittest.cc
index fc435ad0ac849a062d0b21ae50d3c1c080c3a5c9..5cc137fb7ec57d22e7617a434ce1ede01beaf88a 100644
--- a/media/mojo/services/media_service_unittest.cc
+++ b/media/mojo/services/media_service_unittest.cc
@@ -141,7 +141,7 @@ class MediaServiceTest : public service_manager::test::ServiceTest {
     std::vector<mojom::DemuxerStreamPtr> streams;
     streams.push_back(std::move(video_stream_proxy));
     renderer_->Initialize(std::move(client_ptr_info), std::move(streams),
-                          nullptr, base::nullopt, base::nullopt,
+                          nullptr, nullptr, base::nullopt, base::nullopt,
                           base::Bind(&MediaServiceTest::OnRendererInitialized,
                                      base::Unretained(this)));
   }