Remove uses of #pragma once and add PRESUBMIT check.

webrtc/examples/peerconnection/client/peer_connection_client.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_CLIENT_PEER_CONNECTION_CLIENT_H_
 #define WEBRTC_EXAMPLES_PEERCONNECTION_CLIENT_PEER_CONNECTION_CLIENT_H_
-#pragma once
 
 #include <map>
 #include <memory>
 #include <string>
 
 #include "webrtc/base/nethelpers.h"
 #include "webrtc/base/physicalsocketserver.h"
 #include "webrtc/base/signalthread.h"
 #include "webrtc/base/sigslot.h"
 
@@ skipping 90 matching lines @@
   std::string onconnect_data_;
   std::string control_data_;
   std::string notification_data_;
   std::string client_name_;
   Peers peers_;
   State state_;
   int my_id_;
 };
 
 #endif  // WEBRTC_EXAMPLES_PEERCONNECTION_CLIENT_PEER_CONNECTION_CLIENT_H_