Change QuicWallTime to have microsecond granularity.

net/tools/quic/quic_epoll_clock.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/tools/quic/quic_epoll_clock.h"
 
 #include "net/tools/epoll_server/epoll_server.h"
 
 namespace net {
 namespace tools {
 
 QuicEpollClock::QuicEpollClock(EpollServer* epoll_server)
     : epoll_server_(epoll_server) {
 }
 
 QuicEpollClock::~QuicEpollClock() {}
 
 QuicTime QuicEpollClock::ApproximateNow() const {
   return QuicTime::Zero().Add(
       QuicTime::Delta::FromMicroseconds(epoll_server_->ApproximateNowInUsec()));
 }
 
 QuicTime QuicEpollClock::Now() const {
   return QuicTime::Zero().Add(
       QuicTime::Delta::FromMicroseconds(epoll_server_->NowInUsec()));
 }
 
+QuicWallTime QuicEpollClock::WallNow() const {
+  return QuicWallTime::FromUNIXMicroseconds(
+      epoll_server_->ApproximateNowInUsec());
+}
+
 }  // namespace tools
 }  // namespace net