[net] Add Net.UnspecResolvedIPv6 to measure if getaddrinfo resolves IPv6 addresses.

net/base/host_resolver_impl.h

 // 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.
 
 #ifndef NET_BASE_HOST_RESOLVER_IMPL_H_
 #define NET_BASE_HOST_RESOLVER_IMPL_H_
 
 #include <map>
 
 #include "base/basictypes.h"
@@ skipping 230 matching lines @@
 
   // Starts Jobs according to their priority and the configured limits.
   PrioritizedDispatcher dispatcher_;
 
   // Limit on the maximum number of jobs queued in |dispatcher_|.
   size_t max_queued_jobs_;
 
   // Parameters for ProcTask.
   ProcTaskParams proc_params_;
 
+  NetLog* net_log_;
+
   // Address family to use when the request doesn't specify one.
   AddressFamily default_address_family_;
 
   base::WeakPtrFactory<HostResolverImpl> weak_ptr_factory_;
 
   base::WeakPtrFactory<HostResolverImpl> probe_weak_ptr_factory_;
 
   // If present, used by DnsTask and ServeFromHosts to resolve requests.
   scoped_ptr<DnsClient> dns_client_;
 
   // True if received valid config from |dns_config_service_|. Temporary, used
   // to measure performance of DnsConfigService: http://crbug.com/125599
   bool received_dns_config_;
 
   // Number of consecutive failures of DnsTask, counted when fallback succeeds.
   unsigned num_dns_failures_;
 
   // Indicate if probing is done after each network change event to set address
   // family. When false, explicit setting of address family is used and results
   // of the IPv6 probe job are ignored.
   bool ipv6_probe_monitoring_;
 
+  // True iff ProcTask has successfully resolved a hostname known to have IPv6
+  // addresses using ADDRESS_FAMILY_UNSPECIFIED. Reset on IP address change.
+  bool resolved_known_ipv6_hostname_;
+
   // Any resolver flags that should be added to a request by default.
   HostResolverFlags additional_resolver_flags_;
 
-  NetLog* net_log_;
-
   DISALLOW_COPY_AND_ASSIGN(HostResolverImpl);
 };
 
 }  // namespace net
 
 #endif  // NET_BASE_HOST_RESOLVER_IMPL_H_