Measure and export packets sent from send alarm callback.

PiperOrigin-RevId: 553573687

quiche/quic/core/quic_connection.cc

diff --git a/quiche/quic/core/quic_connection.cc b/quiche/quic/core/quic_connection.cc
index cfd5efb..886d884 100644
--- a/quiche/quic/core/quic_connection.cc
+++ b/quiche/quic/core/quic_connection.cc
@@ -126,7 +126,7 @@
 
   void OnAlarm() override {
     QUICHE_DCHECK(connection_->connected());
-    connection_->WriteIfNotBlocked();
+    connection_->OnSendAlarm();
   }
 };
 
@@ -2753,6 +2753,8 @@
   }
 }
 
+void QuicConnection::OnSendAlarm() { WriteIfNotBlocked(); }
+
 void QuicConnection::WriteIfNotBlocked() {
   if (framer().is_processing_packet()) {
     QUIC_BUG(connection_write_mid_packet_processing)

quiche/quic/core/quic_connection.h

diff --git a/quiche/quic/core/quic_connection.h b/quiche/quic/core/quic_connection.h
index 0594e76..04c02e5 100644
--- a/quiche/quic/core/quic_connection.h
+++ b/quiche/quic/core/quic_connection.h
@@ -625,6 +625,9 @@
   // Whether |result| represents a MSG TOO BIG write error.
   bool IsMsgTooBig(const QuicPacketWriter* writer, const WriteResult& result);
 
+  // Called from the SendAlarmDelegate to initiate writing data.
+  virtual void OnSendAlarm();
+
   // If the socket is not blocked, writes queued packets.
   void WriteIfNotBlocked();