relnote: Protected by --quic_fix_cubic_bytes_quantization. Fix CubicBytes Quantization.

net/quic/core/congestion_control/cubic_bytes.cc

Index: net/quic/core/congestion_control/cubic_bytes.cc
diff --git a/net/quic/core/congestion_control/cubic_bytes.cc b/net/quic/core/congestion_control/cubic_bytes.cc
index 7abe9209fe733b3d672cb83abf66df6ab7bdfcd0..388dd008b2c4365bd0690d31aa6f869281ec5360 100644
--- a/net/quic/core/congestion_control/cubic_bytes.cc
+++ b/net/quic/core/congestion_control/cubic_bytes.cc
@@ -41,7 +41,8 @@ CubicBytes::CubicBytes(const QuicClock* clock)
       num_connections_(kDefaultNumConnections),
       epoch_(QuicTime::Zero()),
       last_update_time_(QuicTime::Zero()),
-      fix_convex_mode_(false) {
+      fix_convex_mode_(false),
+      fix_cubic_quantization_(false) {
   Reset();
 }
 
@@ -76,12 +77,17 @@ void CubicBytes::Reset() {
   time_to_origin_point_ = 0;
   last_target_congestion_window_ = 0;
   fix_convex_mode_ = false;
+  fix_cubic_quantization_ = false;
 }
 
 void CubicBytes::SetFixConvexMode(bool fix_convex_mode) {
   fix_convex_mode_ = fix_convex_mode;
 }
 
+void CubicBytes::SetFixCubicQuantization(bool fix_cubic_quantization) {
+  fix_cubic_quantization_ = fix_cubic_quantization;
+}
+
 void CubicBytes::OnApplicationLimited() {
   // When sender is not using the available congestion window, the window does
   // not grow. But to be RTT-independent, Cubic assumes that the sender has been
@@ -158,8 +164,13 @@ QuicByteCount CubicBytes::CongestionWindowAfterAck(
     offset = positive_offset;
   }
   QuicByteCount delta_congestion_window =
-      ((kCubeCongestionWindowScale * offset * offset * offset) >> kCubeScale) *
-      kDefaultTCPMSS;
+      fix_cubic_quantization_
+          ? (kCubeCongestionWindowScale * offset * offset * offset *
+             kDefaultTCPMSS) >>
+                kCubeScale
+          : ((kCubeCongestionWindowScale * offset * offset * offset) >>
+             kCubeScale) *
+                kDefaultTCPMSS;
 
   const bool add_delta = elapsed_time > time_to_origin_point_;
   DCHECK(add_delta ||