De-flake HostResolverImplTest.IsIPv6Reachable.

net/dns/host_resolver_impl.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/dns/host_resolver_impl.h"
 
 #if defined(OS_WIN)
 #include <Winsock2.h>
 #elif defined(OS_POSIX)
 #include <netdb.h>
@@ skipping 2318 matching lines @@
         effective_address_family = ADDRESS_FAMILY_IPV4;
         effective_flags |= HOST_RESOLVER_DEFAULT_FAMILY_SET_DUE_TO_NO_IPV6;
       }
     }
   }
 
   return Key(info.hostname(), effective_address_family, effective_flags);
 }
 
 bool HostResolverImpl::IsIPv6Reachable(const NetLogWithSource& net_log) {
-  base::TimeTicks now = base::TimeTicks::Now();
+  // Cache the result for kIPv6ProbePeriodMs (measured from after
+  // IsGloballyReachable() completes).
   bool cached = true;
-  if ((now - last_ipv6_probe_time_).InMilliseconds() > kIPv6ProbePeriodMs) {
+  if ((base::TimeTicks::Now() - last_ipv6_probe_time_).InMilliseconds() >
+      kIPv6ProbePeriodMs) {
     last_ipv6_probe_result_ =
         IsGloballyReachable(IPAddress(kIPv6ProbeAddress), net_log);
-    last_ipv6_probe_time_ = now;
+    last_ipv6_probe_time_ = base::TimeTicks::Now();
     cached = false;
   }
   net_log.AddEvent(NetLogEventType::HOST_RESOLVER_IMPL_IPV6_REACHABILITY_CHECK,
                    base::Bind(&NetLogIPv6AvailableCallback,
                               last_ipv6_probe_result_, cached));
   return last_ipv6_probe_result_;
 }
 
 void HostResolverImpl::RunLoopbackProbeJob() {
   new LoopbackProbeJob(weak_ptr_factory_.GetWeakPtr(),
@@ skipping 255 matching lines @@
   if (job_)
     job_->CancelRequest(this);
 }
 
 void HostResolverImpl::RequestImpl::ChangeRequestPriority(
     RequestPriority priority) {
   job_->ChangeRequestPriority(this, priority);
 }
 
 }  // namespace net