Add mojo interface+impl creation of audio streams.

content/test/BUILD.gn

Index: content/test/BUILD.gn
diff --git a/content/test/BUILD.gn b/content/test/BUILD.gn
index bff61e7845c1694a5ab24dc41fc667f442567c6b..be2a86460bf49b598902410b084581f84bbc57c3 100644
--- a/content/test/BUILD.gn
+++ b/content/test/BUILD.gn
@@ -1232,12 +1232,14 @@ test("content_unittests") {
     "../browser/renderer_host/media/audio_input_sync_writer_unittest.cc",
     "../browser/renderer_host/media/audio_output_authorization_handler_unittest.cc",
     "../browser/renderer_host/media/audio_output_delegate_impl_unittest.cc",
+    "../browser/renderer_host/media/audio_output_stream_factory_context_impl_unittest.cc",
     "../browser/renderer_host/media/audio_renderer_host_unittest.cc",
     "../browser/renderer_host/media/media_devices_dispatcher_host_unittest.cc",
     "../browser/renderer_host/media/media_devices_manager_unittest.cc",
     "../browser/renderer_host/media/media_stream_dispatcher_host_unittest.cc",
     "../browser/renderer_host/media/media_stream_manager_unittest.cc",
     "../browser/renderer_host/media/media_stream_ui_proxy_unittest.cc",
+    "../browser/renderer_host/media/render_frame_audio_output_stream_factory_unittest.cc",
     "../browser/renderer_host/media/video_capture_buffer_pool_unittest.cc",
     "../browser/renderer_host/media/video_capture_controller_unittest.cc",
     "../browser/renderer_host/media/video_capture_manager_unittest.cc",