ui: Cleanup class/struct forward declarations

media/blink/webmediaplayer_impl_unittest.cc

Index: media/blink/webmediaplayer_impl_unittest.cc
diff --git a/media/blink/webmediaplayer_impl_unittest.cc b/media/blink/webmediaplayer_impl_unittest.cc
index bcbb1500be30f4d51fb3fd016b59bd56fe493fed..9e363e274ee16adbb415bac0efa3a1bcbaec9ba6 100644
--- a/media/blink/webmediaplayer_impl_unittest.cc
+++ b/media/blink/webmediaplayer_impl_unittest.cc
@@ -85,6 +85,7 @@ class DummyWebMediaPlayerClient : public blink::WebMediaPlayerClient {
   void connectedToRemoteDevice() override {}
   void disconnectedFromRemoteDevice() override {}
   void cancelledRemotePlaybackRequest() override {}
+  void remotePlaybackStarted() override {}
   bool isAutoplayingMuted() override { return is_autoplaying_muted_; }
   void requestReload(const blink::WebURL& newUrl) override {}