Remove usage of USE_SYSTEM_PROTOBUF

remoting/protocol/message_serialization.h

 // Copyright 2014 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.
 
 // This file defines utility methods used for encoding and decoding the protocol
 // used in Chromoting.
 
 #ifndef REMOTING_PROTOCOL_MESSAGE_SERIALIZATION_H_
 #define REMOTING_PROTOCOL_MESSAGE_SERIALIZATION_H_
 
 #include "net/base/io_buffer.h"
 #include "remoting/base/compound_buffer.h"
-
-#if defined(USE_SYSTEM_PROTOBUF)
-#include <google/protobuf/message_lite.h>
-#else
 #include "third_party/protobuf/src/google/protobuf/message_lite.h"
-#endif
 
 namespace remoting {
 namespace protocol {
 
 template <class T>
 std::unique_ptr<T> ParseMessage(CompoundBuffer* buffer) {
   std::unique_ptr<T> message(new T());
   CompoundBufferInputStream stream(buffer);
   if (!message->ParseFromZeroCopyStream(&stream)) {
     LOG(WARNING) << "Received message that is not a valid protocol buffer.";
     return nullptr;
   }
   DCHECK_EQ(stream.position(), buffer->total_bytes());
   return message;
 }
 
 // Serialize the Protocol Buffer message and provide sufficient framing for
 // sending it over the wire.
 // This will provide sufficient prefix and suffix for the receiver side to
 // decode the message.
 scoped_refptr<net::IOBufferWithSize> SerializeAndFrameMessage(
     const google::protobuf::MessageLite& msg);
 
 }  // namespace protocol
 }  // namespace remoting
 
 #endif  // REMOTING_PROTOCOL_MESSAGE_SERIALIZATION_H_