Only cancel QUIC alarms if they have been set. Protected behind FLAG_quic_only_cancel_set_alarms

net/quic/quic_alarm.cc

Index: net/quic/quic_alarm.cc
diff --git a/net/quic/quic_alarm.cc b/net/quic/quic_alarm.cc
index b978a146d2e673eee8c9d59fef5a5f4348b56d16..e1f0384138c767dd0a1be416be6932525e5a2e5d 100644
--- a/net/quic/quic_alarm.cc
+++ b/net/quic/quic_alarm.cc
@@ -5,6 +5,7 @@
 #include "net/quic/quic_alarm.h"
 
 #include "base/logging.h"
+#include "net/quic/quic_flags.h"
 
 namespace net {
 
@@ -21,6 +22,10 @@ void QuicAlarm::Set(QuicTime deadline) {
 }
 
 void QuicAlarm::Cancel() {
+  if (FLAGS_quic_only_cancel_set_alarms && !IsSet()) {
+    // Don't try to cancel an alarm that hasn't been set.
+    return;
+  }
   deadline_ = QuicTime::Zero();
   CancelImpl();
 }