Added missing include to fix waterfall compile error.

webrtc/video/video_send_stream.cc

 /*
  *  Copyright (c) 2013 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.
  */
 #include "webrtc/video/video_send_stream.h"
 
 #include <algorithm>
+#include <cmath>
 #include <sstream>
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "webrtc/common_types.h"
 #include "webrtc/base/checks.h"
 #include "webrtc/base/file.h"
 #include "webrtc/base/logging.h"
 #include "webrtc/base/trace_event.h"
@@ skipping 1227 matching lines @@
   const uint16_t mtu = static_cast<uint16_t>(
       config_->rtp.max_packet_size + transport_overhead_bytes_per_packet);
   for (RtpRtcp* rtp_rtcp : rtp_rtcp_modules_) {
     rtp_rtcp->SetTransportOverhead(transport_overhead_bytes_per_packet);
     rtp_rtcp->SetMaxTransferUnit(mtu);
   }
 }
 
 }  // namespace internal
 }  // namespace webrtc