Enable cpplint and fix cpplint errors in webrtc/api

webrtc/api/stats/rtcstats_objects.h

 /*
  *  Copyright 2016 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_STATS_RTCSTATS_OBJECTS_H_
 #define WEBRTC_API_STATS_RTCSTATS_OBJECTS_H_
 
 #include <string>
+#include <vector>
 
 #include "webrtc/api/stats/rtcstats.h"
 
 namespace webrtc {
 
 // https://w3c.github.io/webrtc-pc/#idl-def-rtcdatachannelstate
 struct RTCDataChannelState {
   static const char* kConnecting;
   static const char* kOpen;
   static const char* kClosing;
@@ skipping 386 matching lines @@
   // TODO(hbos): Support enum types? "RTCStatsMember<RTCDtlsTransportState>"?
   RTCStatsMember<std::string> dtls_state;
   RTCStatsMember<std::string> selected_candidate_pair_id;
   RTCStatsMember<std::string> local_certificate_id;
   RTCStatsMember<std::string> remote_certificate_id;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_API_STATS_RTCSTATS_OBJECTS_H_