Mark |Clock*| as |const Clock*| (for some CongestionController and BWE related modules)

webrtc/modules/congestion_controller/delay_based_bwe.cc

 /*
  *  Copyright (c) 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.
  */
 
@@ skipping 212 matching lines @@
   sum_ += bytes;
   return bitrate_sample;
 }
 
 rtc::Optional<uint32_t> DelayBasedBwe::BitrateEstimator::bitrate_bps() const {
   if (bitrate_estimate_ < 0.f)
     return rtc::Optional<uint32_t>();
   return rtc::Optional<uint32_t>(bitrate_estimate_ * 1000);
 }
 
-DelayBasedBwe::DelayBasedBwe(RtcEventLog* event_log, Clock* clock)
+DelayBasedBwe::DelayBasedBwe(RtcEventLog* event_log, const Clock* clock)
     : in_trendline_experiment_(TrendlineFilterExperimentIsEnabled()),
       in_median_slope_experiment_(MedianSlopeFilterExperimentIsEnabled()),
       event_log_(event_log),
       clock_(clock),
       inter_arrival_(),
       kalman_estimator_(),
       trendline_estimator_(),
       detector_(),
       receiver_incoming_bitrate_(),
       last_update_ms_(-1),
@@ skipping 233 matching lines @@
 void DelayBasedBwe::SetMinBitrate(int min_bitrate_bps) {
   // Called from both the configuration thread and the network thread. Shouldn't
   // be called from the network thread in the future.
   rate_control_.SetMinBitrate(min_bitrate_bps);
 }
 
 int64_t DelayBasedBwe::GetProbingIntervalMs() const {
   return probing_interval_estimator_.GetIntervalMs();
 }
 }  // namespace webrtc