Limit QUIC's Cubic CWND increases to 1/2 the bytes acked when in

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 6d40d634e01656b8c2a2cae559fbe6c4466200fe..91924b06e9f6aca1d9dc359a3c45155e2c964960 100644
--- a/net/quic/core/congestion_control/cubic_bytes.cc
+++ b/net/quic/core/congestion_control/cubic_bytes.cc
@@ -9,9 +9,11 @@
 #include <cmath>
 
 #include "base/logging.h"
+#include "net/quic/core/quic_flags.h"
 #include "net/quic/core/quic_protocol.h"
 
 using std::max;
+using std::min;
 
 namespace net {
 
@@ -150,6 +152,12 @@ QuicByteCount CubicBytes::CongestionWindowAfterAck(
 
   QuicByteCount target_congestion_window =
       origin_point_congestion_window_ - delta_congestion_window;
+  if (FLAGS_quic_limit_cubic_cwnd_increase) {
+    // Limit the CWND increase to half the acked bytes.
+    target_congestion_window =
+        min(target_congestion_window,
+            current_congestion_window + acked_bytes_count_ / 2);
+  }
 
   DCHECK_LT(0u, estimated_tcp_congestion_window_);
   // Increase the window by Alpha * 1 MSS of bytes every time we ack an