Update from chromium https://crrev.com/301725/

net/tools/quic/quic_epoll_connection_helper.cc

Index: net/tools/quic/quic_epoll_connection_helper.cc
diff --git a/net/tools/quic/quic_epoll_connection_helper.cc b/net/tools/quic/quic_epoll_connection_helper.cc
index a8321f80198e0c0ac087d9b619beebb24219e0df..b763d822c7ccbd7679dc92c1a09b984b83b78601 100644
--- a/net/tools/quic/quic_epoll_connection_helper.cc
+++ b/net/tools/quic/quic_epoll_connection_helper.cc
@@ -28,14 +28,14 @@ class QuicEpollAlarm : public QuicAlarm {
         epoll_alarm_impl_(this) {}
 
  protected:
-  virtual void SetImpl() override {
+  void SetImpl() override {
     DCHECK(deadline().IsInitialized());
     epoll_server_->RegisterAlarm(
         deadline().Subtract(QuicTime::Zero()).ToMicroseconds(),
         &epoll_alarm_impl_);
   }
 
-  virtual void CancelImpl() override {
+  void CancelImpl() override {
     DCHECK(!deadline().IsInitialized());
     epoll_alarm_impl_.UnregisterIfRegistered();
   }
@@ -45,7 +45,7 @@ class QuicEpollAlarm : public QuicAlarm {
    public:
     explicit EpollAlarmImpl(QuicEpollAlarm* alarm) : alarm_(alarm) {}
 
-    virtual int64 OnAlarm() override {
+    int64 OnAlarm() override {
       EpollAlarm::OnAlarm();
       alarm_->Fire();
       // Fire will take care of registering the alarm, if needed.