Only set one QUIC sending alarm at once. Flag protected by --quic_only_one_sending_alarm.

net/quic/quic_connection.h

Index: net/quic/quic_connection.h
diff --git a/net/quic/quic_connection.h b/net/quic/quic_connection.h
index d1751ad1a04b123b5aa3cb1f12a41a035df7e5bd..a57cc0c01303b3ab5ab6cb4f23a291607edd2471 100644
--- a/net/quic/quic_connection.h
+++ b/net/quic/quic_connection.h
@@ -966,6 +966,8 @@ class NET_EXPORT_PRIVATE QuicConnection
   QuicArenaScopedPtr<QuicAlarm> send_alarm_;
   // An alarm that is scheduled when the connection can still write and there
   // may be more data to send.
+  // TODO(ianswett): Remove resume_writes_alarm when deprecating
+  // FLAGS_quic_only_one_sending_alarm
   QuicArenaScopedPtr<QuicAlarm> resume_writes_alarm_;
   // An alarm that fires when the connection may have timed out.
   QuicArenaScopedPtr<QuicAlarm> timeout_alarm_;