In quicconnection::sendallpendingacks, update instead of set the ack alarm. protected by --gfe2_reloadable_flag_quic_update_ack_alarm_in_send_all_pending_acks.

PiperOrigin-RevId: 312510742
Change-Id: Ieec2e3ffee600202202f6719bf566d9e7ce29685

quic/core/quic_connection.cc

diff --git a/quic/core/quic_connection.cc b/quic/core/quic_connection.cc
index 3519bbc..1ef3cf7 100644
--- a/quic/core/quic_connection.cc
+++ b/quic/core/quic_connection.cc
@@ -4043,7 +4043,13 @@
       uber_received_packet_manager_.GetEarliestAckTimeout();
   if (timeout.IsInitialized()) {
     // If there are ACKs pending, re-arm ack alarm.
-    ack_alarm_->Set(timeout);
+    if (update_ack_alarm_in_send_all_pending_acks_) {
+      QUIC_RELOADABLE_FLAG_COUNT(
+          quic_update_ack_alarm_in_send_all_pending_acks);
+      ack_alarm_->Update(timeout, kAlarmGranularity);
+    } else {
+      ack_alarm_->Set(timeout);
+    }
   }
   // Only try to bundle retransmittable data with ACK frame if default
   // encryption level is forward secure.

quic/core/quic_connection.h

diff --git a/quic/core/quic_connection.h b/quic/core/quic_connection.h
index 87c049b..c1e95f3 100644
--- a/quic/core/quic_connection.h
+++ b/quic/core/quic_connection.h
@@ -1665,6 +1665,9 @@
 
   const bool advance_ack_timeout_update_ =
       GetQuicReloadableFlag(quic_advance_ack_timeout_update);
+
+  const bool update_ack_alarm_in_send_all_pending_acks_ =
+      GetQuicReloadableFlag(quic_update_ack_alarm_in_send_all_pending_acks);
 };
 
 }  // namespace quic