Replace size_t with int in a few media classes.

media/base/data_source.cc

 // Copyright (c) 2011 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 size_t DataSource::kReadError = static_cast<size_t>(-1);
+const int DataSource::kReadError = -1;
 
 DataSourceHost::~DataSourceHost() {}
 
 DataSource::DataSource() : host_(NULL) {}
 
 DataSource::~DataSource() {}
 
 void DataSource::set_host(DataSourceHost* host) {
   DCHECK(host);
   DCHECK(!host_);
   host_ = host;
 }
 
 void DataSource::SetPlaybackRate(float playback_rate) {}
 
 DataSourceHost* DataSource::host() { return host_; }
 
 }  // namespace media