Deprecate gfe2_reloadable_flag_quic_delay_initial_ack

PiperOrigin-RevId: 372931685

quic/core/quic_flags_list.h

diff --git a/quic/core/quic_flags_list.h b/quic/core/quic_flags_list.h
index 3861629..0608993 100644
--- a/quic/core/quic_flags_list.h
+++ b/quic/core/quic_flags_list.h
@@ -25,7 +25,6 @@
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_default_on_pto, false)
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_default_to_bbr, false)
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_default_to_bbr_v2, false)
-QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_delay_initial_ack, true)
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_deprecate_incoming_connection_ids, true)
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_disable_server_blackhole_detection, false)
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_disable_version_draft_29, false)

quic/core/uber_received_packet_manager.cc

diff --git a/quic/core/uber_received_packet_manager.cc b/quic/core/uber_received_packet_manager.cc
index 5ed0e08..8f20b33 100644
--- a/quic/core/uber_received_packet_manager.cc
+++ b/quic/core/uber_received_packet_manager.cc
@@ -120,14 +120,11 @@
   }
   // In IETF QUIC, the peer is expected to acknowledge packets in Initial and
   // Handshake packets with minimal delay.
-  if (!GetQuicReloadableFlag(quic_delay_initial_ack) ||
-      perspective == Perspective::IS_CLIENT) {
+  if (perspective == Perspective::IS_CLIENT) {
     // Delay the first server ACK, because server ACKs are padded to
     // full size and count towards the amplification limit.
     received_packet_managers_[INITIAL_DATA].set_local_max_ack_delay(
         kAlarmGranularity);
-  } else {
-    QUIC_RELOADABLE_FLAG_COUNT(quic_delay_initial_ack);
   }
   received_packet_managers_[HANDSHAKE_DATA].set_local_max_ack_delay(
       kAlarmGranularity);

quic/core/uber_received_packet_manager_test.cc

diff --git a/quic/core/uber_received_packet_manager_test.cc b/quic/core/uber_received_packet_manager_test.cc
index 05e4a33..cf612fe 100644
--- a/quic/core/uber_received_packet_manager_test.cc
+++ b/quic/core/uber_received_packet_manager_test.cc
@@ -478,17 +478,10 @@
   MaybeUpdateAckTimeout(kInstigateAck, ENCRYPTION_INITIAL, 3);
   EXPECT_TRUE(HasPendingAck());
   // Delayed ack is scheduled.
-  if (GetQuicReloadableFlag(quic_delay_initial_ack)) {
-    CheckAckTimeout(clock_.ApproximateNow() +
-                    QuicTime::Delta::FromMilliseconds(25));
-    // Send delayed handshake data ACK.
-    clock_.AdvanceTime(QuicTime::Delta::FromMilliseconds(25));
-  } else {
-    CheckAckTimeout(clock_.ApproximateNow() +
-                    QuicTime::Delta::FromMilliseconds(1));
-    // Send delayed handshake data ACK.
-    clock_.AdvanceTime(QuicTime::Delta::FromMilliseconds(1));
-  }
+  CheckAckTimeout(clock_.ApproximateNow() +
+                  QuicTime::Delta::FromMilliseconds(25));
+  // Send delayed handshake data ACK.
+  clock_.AdvanceTime(QuicTime::Delta::FromMilliseconds(25));
   CheckAckTimeout(clock_.ApproximateNow());
   EXPECT_FALSE(HasPendingAck());