DNS: Let requests specify a callback for future cache hits

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 216 matching lines @@
 
 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())
       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,
                           const Entry* old_entry,
                           const Entry& new_entry) {
   CACHE_HISTOGRAM_ENUM("Set", outcome, MAX_SET_OUTCOME);
   switch (outcome) {
@@ skipping 86 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