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

net/dns/dns_config_service_posix.h

Index: net/dns/dns_config_service_posix.h
diff --git a/net/dns/dns_config_service_posix.h b/net/dns/dns_config_service_posix.h
index d66002aedb2a04ee31c6c45ea25262537b8de45f..6c1bc08ec54beccfe7e5d06fb9d3108b55f8be3b 100644
--- a/net/dns/dns_config_service_posix.h
+++ b/net/dns/dns_config_service_posix.h
@@ -36,8 +36,21 @@ class NET_EXPORT_PRIVATE DnsConfigServicePosix : public DnsConfigService {
   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