Revert of Refactor NACK bitrate allocation

webrtc/base/rate_statistics.cc

Index: webrtc/base/rate_statistics.cc
diff --git a/webrtc/base/rate_statistics.cc b/webrtc/base/rate_statistics.cc
index 3122dbb3e690611bbaf80b39711e9c336d74b60a..1fd63cc6d2a071251edb0a9f4f3744fd700571f2 100644
--- a/webrtc/base/rate_statistics.cc
+++ b/webrtc/base/rate_statistics.cc
@@ -61,10 +61,8 @@
   ++num_samples_;
 }
 
-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);
+rtc::Optional<uint32_t> RateStatistics::Rate(int64_t now_ms) {
+  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.
@@ -114,7 +112,7 @@
   return true;
 }
 
-bool RateStatistics::IsInitialized() const {
+bool RateStatistics::IsInitialized() {
   return oldest_time_ != -max_window_size_ms_;
 }