DNS: Expose stale results through HostResolverImpl.

net/dns/host_resolver_impl.cc

Index: net/dns/host_resolver_impl.cc
diff --git a/net/dns/host_resolver_impl.cc b/net/dns/host_resolver_impl.cc
index a224b8c4e38a87d943fef29f7494c738186e1096..0cc8c683d864666a7f35971f9e81d36bc8a8a377 100644
--- a/net/dns/host_resolver_impl.cc
+++ b/net/dns/host_resolver_impl.cc
@@ -1949,7 +1949,8 @@ int HostResolverImpl::Resolve(const RequestInfo& info,
   // outstanding jobs map.
   Key key = GetEffectiveKeyForRequest(info, ip_address_ptr, source_net_log);
 
-  int rv = ResolveHelper(key, info, ip_address_ptr, addresses, source_net_log);
+  int rv = ResolveHelper(key, info, ip_address_ptr, addresses, nullptr,
+                         source_net_log);
   if (rv != ERR_DNS_CACHE_MISS) {
     LogFinishRequest(source_net_log, info, rv);
     RecordTotalTime(HaveDnsConfig(), info.is_speculative(), base::TimeDelta());
@@ -1997,6 +1998,7 @@ int HostResolverImpl::ResolveHelper(const Key& key,
                                     const RequestInfo& info,
                                     const IPAddress* ip_address,
                                     AddressList* addresses,
+                                    HostCache::StaleEntryInfo* stale_info,
                                     const BoundNetLog& source_net_log) {
   // The result of |getaddrinfo| for empty hosts is inconsistent across systems.
   // On Windows it gives the default interface's address, whereas on Linux it
@@ -2007,7 +2009,7 @@ int HostResolverImpl::ResolveHelper(const Key& key,
   int net_error = ERR_UNEXPECTED;
   if (ResolveAsIP(key, info, ip_address, &net_error, addresses))
     return net_error;
-  if (ServeFromCache(key, info, &net_error, addresses)) {
+  if (ServeFromCache(key, info, &net_error, addresses, stale_info)) {
     source_net_log.AddEvent(NetLog::TYPE_HOST_RESOLVER_IMPL_CACHE_HIT);
     return net_error;
   }
@@ -2027,6 +2029,14 @@ int HostResolverImpl::ResolveHelper(const Key& key,
 int HostResolverImpl::ResolveFromCache(const RequestInfo& info,
                                        AddressList* addresses,
                                        const BoundNetLog& source_net_log) {
+  return ResolveStaleFromCache(info, addresses, nullptr, source_net_log);
+}
+
+int HostResolverImpl::ResolveStaleFromCache(
+    const RequestInfo& info,
+    AddressList* addresses,
+    HostCache::StaleEntryInfo* stale_info,
+    const BoundNetLog& source_net_log) {
   DCHECK(CalledOnValidThread());
   DCHECK(addresses);
 
@@ -2040,7 +2050,8 @@ int HostResolverImpl::ResolveFromCache(const RequestInfo& info,
 
   Key key = GetEffectiveKeyForRequest(info, ip_address_ptr, source_net_log);
 
-  int rv = ResolveHelper(key, info, ip_address_ptr, addresses, source_net_log);
+  int rv = ResolveHelper(key, info, ip_address_ptr, addresses, stale_info,
+                         source_net_log);
   LogFinishRequest(source_net_log, info, rv);
   return rv;
 }
@@ -2110,14 +2121,18 @@ bool HostResolverImpl::ResolveAsIP(const Key& key,
 bool HostResolverImpl::ServeFromCache(const Key& key,
                                       const RequestInfo& info,
                                       int* net_error,
-                                      AddressList* addresses) {
+                                      AddressList* addresses,
+                                      HostCache::StaleEntryInfo* stale_info) {
   DCHECK(addresses);
   DCHECK(net_error);
   if (!info.allow_cached_response() || !cache_.get())
     return false;
 
-  const HostCache::Entry* cache_entry = cache_->Lookup(
-      key, base::TimeTicks::Now());
+  const HostCache::Entry* cache_entry;
+  if (stale_info)
+    cache_entry = cache_->LookupStale(key, base::TimeTicks::Now(), stale_info);
+  else
+    cache_entry = cache_->Lookup(key, base::TimeTicks::Now());
   if (!cache_entry)
     return false;