Cleanup usage of scoped_ptr<> in remoting for C++11

remoting/codec/audio_decoder_verbatim.cc

 // Copyright (c) 2012 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 "remoting/codec/audio_decoder_verbatim.h"
 
 #include "base/logging.h"
 #include "remoting/proto/audio.pb.h"
 
 namespace remoting {
 
 AudioDecoderVerbatim::AudioDecoderVerbatim() {
 }
 
 AudioDecoderVerbatim::~AudioDecoderVerbatim() {
 }
 
 scoped_ptr<AudioPacket> AudioDecoderVerbatim::Decode(
     scoped_ptr<AudioPacket> packet) {
   // Return a null scoped_ptr if we get a corrupted packet.
   if ((packet->encoding() != AudioPacket::ENCODING_RAW) ||
       (packet->data_size() != 1) ||
       (packet->sampling_rate() == AudioPacket::SAMPLING_RATE_INVALID) ||
       (packet->bytes_per_sample() != AudioPacket::BYTES_PER_SAMPLE_2) ||
       (packet->channels() != AudioPacket::CHANNELS_STEREO) ||
       (packet->data(0).size() %
        (AudioPacket::CHANNELS_STEREO * AudioPacket::BYTES_PER_SAMPLE_2) != 0)) {
     LOG(WARNING) << "Verbatim decoder received an invalid packet.";
-    return scoped_ptr<AudioPacket>();
+    return nullptr;
   }
   return packet.Pass();
 }
 
 }  // namespace remoting