fix build when ffmpeg, libvpx and libwebm are disabled

content/renderer/media/media_recorder_handler.h

 // 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.
 
 #ifndef CONTENT_RENDERER_MEDIA_MEDIA_RECORDER_HANDLER_H_
 #define CONTENT_RENDERER_MEDIA_MEDIA_RECORDER_HANDLER_H_
 
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_vector.h"
 #include "base/memory/weak_ptr.h"
@@ skipping 69 matching lines @@
   base::TimeTicks slice_origin_timestamp_;
 
   bool recording_;
   blink::WebMediaStream media_stream_;  // The MediaStream being recorded.
 
   // |client_| is a weak pointer, and is valid for the lifetime of this object.
   blink::WebMediaRecorderHandlerClient* client_;
 
   ScopedVector<VideoTrackRecorder> video_recorders_;
 
+#if !defined(MEDIA_DISABLE_LIBWEBM)
   // Worker class doing the actual Webm Muxing work.
   scoped_ptr<media::WebmMuxer> webm_muxer_;
+#endif
 
   base::WeakPtrFactory<MediaRecorderHandler> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaRecorderHandler);
 };
 
 }  // namespace content
 #endif  // CONTENT_RENDERER_MEDIA_MEDIA_RECORDER_HANDLER_H_