Disable background video track behind a feature flag

content/renderer/media/webmediaplayer_ms_unittest.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <stddef.h>
 
 #include "base/run_loop.h"
 #include "base/single_thread_task_runner.h"
 #include "content/public/renderer/media_stream_renderer_factory.h"
 #include "content/renderer/media/webmediaplayer_ms.h"
@@ skipping 409 matching lines @@
   void removeVideoTrack(blink::WebMediaPlayer::TrackId) override {}
   void addTextTrack(blink::WebInbandTextTrack*) override {}
   void removeTextTrack(blink::WebInbandTextTrack*) override {}
   void mediaSourceOpened(blink::WebMediaSource*) override {}
   void requestSeek(double) override {}
   void remoteRouteAvailabilityChanged(bool) override {}
   void connectedToRemoteDevice() override {}
   void disconnectedFromRemoteDevice() override {}
   void cancelledRemotePlaybackRequest() override {}
   void remotePlaybackStarted() override {}
+  void hidden() override {}
+  void shown() override {}
   bool isAutoplayingMuted() override { return false; }
   void requestReload(const blink::WebURL& newUrl) override {}
 
   // Implementation of cc::VideoFrameProvider::Client
   void StopUsingProvider() override;
   void StartRendering() override;
   void StopRendering() override;
   void DidReceiveFrame() override {}
 
   // For test use
@@ skipping 477 matching lines @@
   // OnShown() should restart after a forced suspension.
   player_->OnShown();
   EXPECT_FALSE(player_->paused());
   EXPECT_CALL(*this, DoSetWebLayer(false));
 
   base::RunLoop().RunUntilIdle();
 }
 #endif
 
 }  // namespace content