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

net/tools/quic/quic_epoll_clock.h

Index: net/tools/quic/quic_epoll_clock.h
diff --git a/net/tools/quic/quic_epoll_clock.h b/net/tools/quic/quic_epoll_clock.h
index 4eebefbab7c1971834deb25b6c8ab47a44c4a029..c5a1390bd242aa1625edb3c3d9b927fe696286ee 100644
--- a/net/tools/quic/quic_epoll_clock.h
+++ b/net/tools/quic/quic_epoll_clock.h
@@ -21,14 +21,14 @@ namespace tools {
 class QuicEpollClock : public QuicClock {
  public:
   explicit QuicEpollClock(EpollServer* epoll_server);
-  virtual ~QuicEpollClock();
+  ~QuicEpollClock() override;
 
   // Returns the approximate current time as a QuicTime object.
-  virtual QuicTime ApproximateNow() const override;
+  QuicTime ApproximateNow() const override;
 
   // Returns the current time as a QuicTime object.
   // Note: this use significant resources please use only if needed.
-  virtual QuicTime Now() const override;
+  QuicTime Now() const override;
 
  protected:
   EpollServer* epoll_server_;