ui: Cleanup class/struct forward declarations

services/video_capture/BUILD.gn

Index: services/video_capture/BUILD.gn
diff --git a/services/video_capture/BUILD.gn b/services/video_capture/BUILD.gn
index 7eda0c4ccf4d8a7058e2b68e4d18a58caa4c6101..3ab4a589ca9cd475a8cec1e828a42eefdc7b9d77 100644
--- a/services/video_capture/BUILD.gn
+++ b/services/video_capture/BUILD.gn
@@ -37,16 +37,18 @@ source_set("lib") {
     "buffer_tracker_factory_impl.h",
     "device_client_media_to_mojo_adapter.cc",
     "device_client_media_to_mojo_adapter.h",
+    "device_factory_media_to_mojo_adapter.cc",
+    "device_factory_media_to_mojo_adapter.h",
     "device_mock_to_media_adapter.cc",
     "device_mock_to_media_adapter.h",
+    "mock_device_factory.cc",
+    "mock_device_factory.h",
     "mojo_shared_memory_buffer_handle.cc",
     "mojo_shared_memory_buffer_handle.h",
     "mojo_shared_memory_buffer_tracker.cc",
     "mojo_shared_memory_buffer_tracker.h",
     "receiver_mojo_to_media_adapter.cc",
     "receiver_mojo_to_media_adapter.h",
-    "video_capture_device_factory_impl.cc",
-    "video_capture_device_factory_impl.h",
     "video_capture_device_proxy_impl.cc",
     "video_capture_device_proxy_impl.h",
   ]