[net/dns] Instrument DnsConfigService to measure performance and failures.

net/dns/dns_config_service_posix.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_DNS_DNS_CONFIG_SERVICE_POSIX_H_
 #define NET_DNS_DNS_CONFIG_SERVICE_POSIX_H_
 #pragma once
 
 #include <sys/types.h>
 #include <netinet/in.h>
@@ skipping 18 matching lines @@
  private:
   // NetworkChangeNotifier::DNSObserver:
   virtual void OnDNSChanged(unsigned detail) OVERRIDE;
 
   scoped_refptr<SerialWorker> config_reader_;
   scoped_refptr<SerialWorker> hosts_reader_;
 
   DISALLOW_COPY_AND_ASSIGN(DnsConfigServicePosix);
 };
 
+enum ConfigParsePosixResult {
+  CONFIG_PARSE_POSIX_OK = 0,
+  CONFIG_PARSE_POSIX_RES_INIT_FAILED,
+  CONFIG_PARSE_POSIX_RES_INIT_UNSET,
+  CONFIG_PARSE_POSIX_BAD_ADDRESS,
+  CONFIG_PARSE_POSIX_BAD_EXT_STRUCT,
+  CONFIG_PARSE_POSIX_NULL_ADDRESS,
+  CONFIG_PARSE_POSIX_NO_NAMESERVERS,
+  CONFIG_PARSE_POSIX_MISSING_OPTIONS,
+  CONFIG_PARSE_POSIX_UNHANDLED_OPTIONS,
+  CONFIG_PARSE_POSIX_MAX  // Bounding values for enumeration.
+};
+
 // Fills in |dns_config| from |res|.
-bool NET_EXPORT_PRIVATE ConvertResStateToDnsConfig(
+ConfigParsePosixResult NET_EXPORT_PRIVATE ConvertResStateToDnsConfig(
     const struct __res_state& res, DnsConfig* dns_config);
 
 }  // namespace internal
 
 }  // namespace net
 
 #endif  // NET_DNS_DNS_CONFIG_SERVICE_POSIX_H_