Separate DemuxerHost from DataSourceHost.

media/base/data_source.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 "media/base/data_source.h"
 
 #include "base/logging.h"
 
 namespace media {
 
 // static
 const int DataSource::kReadError = -1;
 
 DataSourceHost::~DataSourceHost() {}
 
-DataSource::DataSource() : host_(NULL) {}
+DataSource::DataSource() {}
 
 DataSource::~DataSource() {}
 
-void DataSource::set_host(DataSourceHost* host) {
-  DCHECK(host);
-  DCHECK(!host_);
-  host_ = host;
-}
-
-DataSourceHost* DataSource::host() { return host_; }
-
 }  // namespace media