Use overloaded operators with QuicTime for addition, subtraction and scalar

net/quic/congestion_control/cubic_bytes.cc

 // Copyright (c) 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/quic/congestion_control/cubic_bytes.h"
 
 #include <stdint.h>
 #include <algorithm>
 #include <cmath>
 
@@ skipping 94 matching lines @@
 
 QuicByteCount CubicBytes::CongestionWindowAfterAck(
     QuicByteCount acked_bytes,
     QuicByteCount current_congestion_window,
     QuicTime::Delta delay_min) {
   acked_bytes_count_ += acked_bytes;
   QuicTime current_time = clock_->ApproximateNow();
 
   // Cubic is "independent" of RTT, the update is limited by the time elapsed.
   if (last_congestion_window_ == current_congestion_window &&
-      (current_time.Subtract(last_update_time_) <= MaxCubicTimeInterval())) {
+      (current_time - last_update_time_ <= MaxCubicTimeInterval())) {
     return max(last_target_congestion_window_,
                estimated_tcp_congestion_window_);
   }
   last_congestion_window_ = current_congestion_window;
   last_update_time_ = current_time;
 
   if (!epoch_.IsInitialized()) {
     // First ACK after a loss event.
     DVLOG(1) << "Start of epoch";
     epoch_ = current_time;             // Start of epoch.
     acked_bytes_count_ = acked_bytes;  // Reset count.
     // Reset estimated_tcp_congestion_window_ to be in sync with cubic.
     estimated_tcp_congestion_window_ = current_congestion_window;
     if (last_max_congestion_window_ <= current_congestion_window) {
       time_to_origin_point_ = 0;
       origin_point_congestion_window_ = current_congestion_window;
     } else {
       time_to_origin_point_ = static_cast<uint32_t>(
           cbrt(kCubeFactor *
                (last_max_congestion_window_ - current_congestion_window)));
       origin_point_congestion_window_ = last_max_congestion_window_;
     }
   }
   // Change the time unit from microseconds to 2^10 fractions per second. Take
   // the round trip time in account. This is done to allow us to use shift as a
   // divide operator.
   int64_t elapsed_time =
-      (current_time.Add(delay_min).Subtract(epoch_).ToMicroseconds() << 10) /
+      ((current_time + delay_min - epoch_).ToMicroseconds() << 10) /
       kNumMicrosPerSecond;
 
   int64_t offset = time_to_origin_point_ - elapsed_time;
   QuicByteCount delta_congestion_window =
       ((kCubeCongestionWindowScale * offset * offset * offset) >> kCubeScale) *
       kDefaultTCPMSS;
 
   QuicByteCount target_congestion_window =
       origin_point_congestion_window_ - delta_congestion_window;
 
@@ skipping 12 matching lines @@
   // congestion_window, use highest (fastest).
   if (target_congestion_window < estimated_tcp_congestion_window_) {
     target_congestion_window = estimated_tcp_congestion_window_;
   }
 
   DVLOG(1) << "Final target congestion_window: " << target_congestion_window;
   return target_congestion_window;
 }
 
 }  // namespace net