HostCache: always evict stale entries before valid entries

net/dns/host_cache.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_cache.h"
 
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram_macros.h"
@@ skipping 235 matching lines @@
   if ((max_entries == 0) || (max_entries > kSaneMaxEntries))
     max_entries = kDefaultMaxEntries;
   return base::WrapUnique(new HostCache(max_entries));
 }
 
 void HostCache::EvictOneEntry(base::TimeTicks now) {
   DCHECK_LT(0u, entries_.size());
 
   auto oldest_it = entries_.begin();
   for (auto it = entries_.begin(); it != entries_.end(); ++it) {
-    if (it->second.expires() < oldest_it->second.expires())
+    if ((it->second.expires() < oldest_it->second.expires()) &&
+        (it->second.IsStale(now, network_changes_) ||
+         !oldest_it->second.IsStale(now, network_changes_))) {
       oldest_it = it;
+    }
   }
 
   if (!eviction_callback_.is_null())
     eviction_callback_.Run(oldest_it->first, oldest_it->second);
   RecordErase(ERASE_EVICT, now, oldest_it->second);
   entries_.erase(oldest_it);
 }
 
 void HostCache::RecordSet(SetOutcome outcome,
                           base::TimeTicks now,
@@ skipping 90 matching lines @@
     CACHE_HISTOGRAM_TIME("EraseValid.ValidFor", -stale.expired_by);
   }
 }
 
 void HostCache::RecordEraseAll(EraseReason reason, base::TimeTicks now) {
   for (const auto& it : entries_)
     RecordErase(reason, now, it.second);
 }
 
 }  // namespace net