Remove media::VideoDecodeContext as it has no implementation and is unused.

media/tools/player_wtl/movie.cc

Index: media/tools/player_wtl/movie.cc
diff --git a/media/tools/player_wtl/movie.cc b/media/tools/player_wtl/movie.cc
index 3552c573a2047c1b41308aad2841cafd41f6727b..9b298ca878cdb6785c34cad866704b98087a2ecb 100644
--- a/media/tools/player_wtl/movie.cc
+++ b/media/tools/player_wtl/movie.cc
@@ -75,7 +75,7 @@ bool Movie::Open(const wchar_t* url, WtlVideoRenderer* video_renderer) {
   collection->AddAudioDecoder(new FFmpegAudioDecoder(
       message_loop_factory_->GetMessageLoop("AudioDecoderThread")));
   collection->AddVideoDecoder(new FFmpegVideoDecoder(
-      message_loop_factory_->GetMessageLoop("VideoDecoderThread"), NULL));
+      message_loop_factory_->GetMessageLoop("VideoDecoderThread")));
 
   if (enable_audio_) {
     collection->AddAudioRenderer(new ReferenceAudioRenderer());