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

net/base/host_resolver_impl.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_resolver_impl.h"
 
 #if defined(OS_WIN)
 #include <Winsock2.h>
 #elif defined(OS_POSIX)
 #include <netdb.h>
@@ skipping 1365 matching lines @@
 
     net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HOST_RESOLVER_IMPL_JOB,
                                       net_error);
 
     DCHECK(!requests_.empty());
 
     if (net_error == OK) {
       SetPortOnAddressList(requests_->front()->info().port(), &list);
       // Record this histogram here, when we know the system has a valid DNS
       // configuration.
-      UMA_HISTOGRAM_ENUMERATION("AsyncDNS.HaveDnsConfig",
-                                resolver_->received_dns_config_ ? 1 : 0,
-                                2);
+      UMA_HISTOGRAM_BOOLEAN("AsyncDNS.HaveDnsConfig",
+                            resolver_->received_dns_config_);
     }
 
     if ((net_error != ERR_ABORTED) &&
         (net_error != ERR_HOST_RESOLVER_QUEUE_TOO_LARGE)) {
       resolver_->CacheResult(key_, net_error, list, ttl);
     }
 
     // Complete all of the requests that were attached to the job.
     for (RequestsList::const_iterator it = requests_.begin();
          it != requests_.end(); ++it) {
@@ skipping 531 matching lines @@
     if (self)
       TryServingAllJobsFromHosts();
   }
 }
 
 bool HostResolverImpl::HaveDnsConfig() const {
   return (dns_client_.get() != NULL) && (dns_client_->GetConfig() != NULL);
 }
 
 }  // namespace net