Enable cpplint and fix cpplint errors in webrtc/api

webrtc/api/peerconnectionproxy.h

 /*
  *  Copyright 2012 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_API_PEERCONNECTIONPROXY_H_
 #define WEBRTC_API_PEERCONNECTIONPROXY_H_
 
+#include <string>
+#include <vector>
+
 #include "webrtc/api/peerconnectioninterface.h"
 #include "webrtc/api/proxy.h"
 
 namespace webrtc {
 
 // Define proxy for PeerConnectionInterface.
 BEGIN_SIGNALING_PROXY_MAP(PeerConnection)
   PROXY_SIGNALING_THREAD_DESTRUCTOR()
   PROXY_METHOD0(rtc::scoped_refptr<StreamCollectionInterface>, local_streams)
   PROXY_METHOD0(rtc::scoped_refptr<StreamCollectionInterface>, remote_streams)
@@ skipping 76 matching lines @@
   PROXY_METHOD0(IceConnectionState, ice_connection_state)
   PROXY_METHOD0(IceGatheringState, ice_gathering_state)
   PROXY_METHOD2(bool, StartRtcEventLog, rtc::PlatformFile, int64_t)
   PROXY_METHOD0(void, StopRtcEventLog)
   PROXY_METHOD0(void, Close)
 END_PROXY_MAP()
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_API_PEERCONNECTIONPROXY_H_