Reland of actor NACK bitrate allocation

webrtc/base/rate_statistics.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.
  */
 
@@ skipping 43 matching lines @@
   RTC_DCHECK_LT(now_offset, max_window_size_ms_);
   uint32_t index = oldest_index_ + now_offset;
   if (index >= max_window_size_ms_)
     index -= max_window_size_ms_;
   buckets_[index].sum += count;
   ++buckets_[index].samples;
   accumulated_count_ += count;
   ++num_samples_;
 }
 
-rtc::Optional<uint32_t> RateStatistics::Rate(int64_t now_ms) {
-  EraseOld(now_ms);
+rtc::Optional<uint32_t> RateStatistics::Rate(int64_t now_ms) const {
+  // Yeah, this const_cast ain't pretty, but the alternative is to declare most
+  // of the members as mutable...
+  const_cast<RateStatistics*>(this)->EraseOld(now_ms);
 
   // If window is a single bucket or there is only one sample in a data set that
   // has not grown to the full window size, treat this as rate unavailable.
   int64_t active_window_size = now_ms - oldest_time_ + 1;
   if (num_samples_ == 0 || active_window_size <= 1 ||
       (num_samples_ <= 1 && active_window_size < current_window_size_ms_)) {
     return rtc::Optional<uint32_t>();
   }
 
   float scale = scale_ / active_window_size;
@@ skipping 29 matching lines @@
 
 bool RateStatistics::SetWindowSize(int64_t window_size_ms, int64_t now_ms) {
   if (window_size_ms <= 0 || window_size_ms > max_window_size_ms_)
     return false;
 
   current_window_size_ms_ = window_size_ms;
   EraseOld(now_ms);
   return true;
 }
 
-bool RateStatistics::IsInitialized() {
+bool RateStatistics::IsInitialized() const {
   return oldest_time_ != -max_window_size_ms_;
 }
 
 }  // namespace webrtc