[net] Add AsyncDNS.TTL histogram.

net/base/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/base/host_cache.h"
 
 #include "base/logging.h"
 #include "net/base/net_errors.h"
 
 namespace net {
 
 //-----------------------------------------------------------------------------
 
+HostCache::Entry::Entry(int error, const AddressList& addrlist,
+                        base::TimeDelta ttl)
+    : error(error),
+      addrlist(addrlist),
+      ttl(ttl) {
+  DCHECK(ttl >= base::TimeDelta());
+}
+
 HostCache::Entry::Entry(int error, const AddressList& addrlist)
     : error(error),
-      addrlist(addrlist) {
+      addrlist(addrlist),
+      ttl(base::TimeDelta::FromSeconds(-1)) {
 }
 
 HostCache::Entry::~Entry() {
 }
 
 //-----------------------------------------------------------------------------
 
 HostCache::HostCache(size_t max_entries)
     : entries_(max_entries) {
 }
 
 HostCache::~HostCache() {
 }
 
 const HostCache::Entry* HostCache::Lookup(const Key& key,
                                           base::TimeTicks now) {
   DCHECK(CalledOnValidThread());
   if (caching_is_disabled())
     return NULL;
 
   return entries_.Get(key, now);
 }
 
 void HostCache::Set(const Key& key,
-                    int error,
-                    const AddressList& addrlist,
+                    const Entry& entry,
                     base::TimeTicks now,
                     base::TimeDelta ttl) {
   DCHECK(CalledOnValidThread());
   if (caching_is_disabled())
     return;
 
-  entries_.Put(key, Entry(error, addrlist), now, now + ttl);
+  entries_.Put(key, entry, now, now + ttl);
 }
 
 void HostCache::clear() {
   DCHECK(CalledOnValidThread());
   entries_.Clear();
 }
 
 size_t HostCache::size() const {
   DCHECK(CalledOnValidThread());
   return entries_.size();
@@ skipping 17 matching lines @@
   // http://crbug.com/143454
   // TODO(szym): Determine the best size. http://crbug.com/114277
   static const size_t kMaxHostCacheEntries = 1000;
 #else
   static const size_t kMaxHostCacheEntries = 100;
 #endif
   return new HostCache(kMaxHostCacheEntries);
 }
 
 }  // namespace net