Deprecate FLAGS_reset_cubic_epoch_when_app_limited.

net/quic/congestion_control/tcp_cubic_bytes_sender.cc

Index: net/quic/congestion_control/tcp_cubic_bytes_sender.cc
diff --git a/net/quic/congestion_control/tcp_cubic_bytes_sender.cc b/net/quic/congestion_control/tcp_cubic_bytes_sender.cc
index c34d448db1b402ec795a5f9764d70743cd85ecef..0dd8169f9bdbf578cbedac8408295ab098c7bc6f 100644
--- a/net/quic/congestion_control/tcp_cubic_bytes_sender.cc
+++ b/net/quic/congestion_control/tcp_cubic_bytes_sender.cc
@@ -295,12 +295,10 @@ void TcpCubicBytesSender::MaybeIncreaseCwnd(
     QuicByteCount acked_bytes,
     QuicByteCount bytes_in_flight) {
   LOG_IF(DFATAL, InRecovery()) << "Never increase the CWND during recovery.";
+  // Do not increase the congestion window unless the sender is close to using
+  // the current window.
   if (!IsCwndLimited(bytes_in_flight)) {
-    // Do not increase the congestion window unless the sender is close to using
-    // the current window.
-    if (FLAGS_reset_cubic_epoch_when_app_limited) {
-      cubic_.OnApplicationLimited();
-    }
+    cubic_.OnApplicationLimited();
     return;
   }
   if (congestion_window_ >= max_congestion_window_) {