Convert //media/filters from scoped_ptr to std::unique_ptr

media/filters/opus_audio_decoder.h

Index: media/filters/opus_audio_decoder.h
diff --git a/media/filters/opus_audio_decoder.h b/media/filters/opus_audio_decoder.h
index 8cb94a9c8dbef6a0f3997bf9e45af191ddbec998..8ad1a9782a49b85131ad9d3ddcd6264a84035b6c 100644
--- a/media/filters/opus_audio_decoder.h
+++ b/media/filters/opus_audio_decoder.h
@@ -58,7 +58,7 @@ class MEDIA_EXPORT OpusAudioDecoder : public AudioDecoder {
   AudioDecoderConfig config_;
   OutputCB output_cb_;
   OpusMSDecoder* opus_decoder_;
-  scoped_ptr<AudioDiscardHelper> discard_helper_;
+  std::unique_ptr<AudioDiscardHelper> discard_helper_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(OpusAudioDecoder);
 };