Remove uses of #pragma once and add PRESUBMIT check.

webrtc/examples/peerconnection/server/peer_channel.h

 /*
  *  Copyright 2011 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #ifndef WEBRTC_EXAMPLES_PEERCONNECTION_SERVER_PEER_CHANNEL_H_
 #define WEBRTC_EXAMPLES_PEERCONNECTION_SERVER_PEER_CHANNEL_H_
-#pragma once
 
 #include <time.h>
 
 #include <queue>
 #include <string>
 #include <vector>
 
 class DataSocket;
 
 // Represents a single peer connected to the server.
@@ skipping 87 matching lines @@
 
   // Builds a simple list of "name,id\n" entries for each member.
   std::string BuildResponseForNewMember(const ChannelMember& member,
                                         std::string* content_type);
 
  protected:
   Members members_;
 };
 
 #endif  // WEBRTC_EXAMPLES_PEERCONNECTION_SERVER_PEER_CHANNEL_H_