gfe-relnote: (n/a) Make QUIC BBRv2's initial ack height filter window tunable by flag --quic_bbr2_default_initial_ack_height_filter_window. No behavior change when the flag is at its default value.

PiperOrigin-RevId: 289638266
Change-Id: I3a781919cf5943be0fc1551697c13573b52f7a10

quic/core/congestion_control/bbr2_misc.h

diff --git a/quic/core/congestion_control/bbr2_misc.h b/quic/core/congestion_control/bbr2_misc.h
index b97184b..5c8c0e2 100644
--- a/quic/core/congestion_control/bbr2_misc.h
+++ b/quic/core/congestion_control/bbr2_misc.h
@@ -142,7 +142,8 @@
    */
 
   // The initial value of the max ack height filter's window length.
-  QuicRoundTripCount initial_max_ack_height_filter_window = 10;
+  QuicRoundTripCount initial_max_ack_height_filter_window =
+      GetQuicFlag(FLAGS_quic_bbr2_default_initial_ack_height_filter_window);
 
   // Fraction of unutilized headroom to try to leave in path upon high loss.
   float inflight_hi_headroom =