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

webrtc/base/rate_limiter.h

 /*
  *  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.
  */
 
 #ifndef WEBRTC_BASE_RATE_LIMITER_H_
 #define WEBRTC_BASE_RATE_LIMITER_H_
 
 #include <limits>
 
 #include "webrtc/base/constructormagic.h"
 #include "webrtc/base/criticalsection.h"
 #include "webrtc/base/rate_statistics.h"
 
 namespace webrtc {
 
 class Clock;
 
 // Class used to limit a bitrate, making sure the average does not exceed a
 // maximum as measured over a sliding window. This class is thread safe; all
 // methods will acquire (the same) lock befeore executing.
 class RateLimiter {
  public:
-  RateLimiter(Clock* clock, int64_t max_window_ms);
+  RateLimiter(const Clock* clock, int64_t max_window_ms);
   ~RateLimiter();
 
   // Try to use rate to send bytes. Returns true on success and if so updates
   // current rate.
   bool TryUseRate(size_t packet_size_bytes);
 
   // Set the maximum bitrate, in bps, that this limiter allows to send.
   void SetMaxRate(uint32_t max_rate_bps);
 
   // Set the window size over which to measure the current bitrate.
   // For example, irt retransmissions, this is typically the RTT.
   // Returns true on success and false if window_size_ms is out of range.
   bool SetWindowSize(int64_t window_size_ms);
 
  private:
-  Clock* const clock_;
+  const Clock* const clock_;
   rtc::CriticalSection lock_;
   RateStatistics current_rate_ GUARDED_BY(lock_);
   int64_t window_size_ms_ GUARDED_BY(lock_);
   uint32_t max_rate_bps_ GUARDED_BY(lock_);
 
   RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(RateLimiter);
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_BASE_RATE_LIMITER_H_