relnote: Use NotifyChangedPriority when updating alarms instead of canceling and reregistering. Gua…

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 3067a29c35c0a76d1308b3e5712e690271970d95..26021fb8893b39fc01e0ee4769c603f41810f871 100644
--- a/net/quic/quic_alarm.cc
+++ b/net/quic/quic_alarm.cc
@@ -39,8 +39,18 @@ void QuicAlarm::Update(QuicTime new_deadline, QuicTime::Delta granularity) {
       granularity.ToMicroseconds()) {
     return;
   }
-  Cancel();
-  Set(new_deadline);
+  if (FLAGS_quic_change_alarms_efficiently) {
+    const bool was_set = IsSet();
+    deadline_ = new_deadline;
+    if (was_set) {
+      UpdateImpl();
+    } else {
+      SetImpl();
+    }
+  } else {
+    Cancel();
+    Set(new_deadline);
+  }
 }
 
 bool QuicAlarm::IsSet() const {
@@ -56,4 +66,16 @@ void QuicAlarm::Fire() {
   delegate_->OnAlarm();
 }
 
+void QuicAlarm::UpdateImpl() {
+  // CancelImpl and SetImpl take the new deadline by way of the deadline_
+  // member, so save and restore deadline_ before canceling.
+  const QuicTime new_deadline = deadline_;
+
+  deadline_ = QuicTime::Zero();
+  CancelImpl();
+
+  deadline_ = new_deadline;
+  SetImpl();

[Ryan Hamilton, 2016/07/19 21:13:38]

Hah! So in chromium UpdateImpl is basically Cancel() / Set(new_deadline)? 

+}
+
 }  // namespace net