[NOT FOR REVIEW] Instrument net/ with trace events.

net/dns/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/dns/host_resolver_impl.h"
 
 #include <utility>
 
 #if defined(OS_WIN)
 #include <Winsock2.h>
@@ skipping 17 matching lines @@
 #include "base/metrics/histogram_macros.h"
 #include "base/metrics/sparse_histogram.h"
 #include "base/profiler/scoped_tracker.h"
 #include "base/single_thread_task_runner.h"
 #include "base/stl_util.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/thread_task_runner_handle.h"
 #include "base/threading/worker_pool.h"
 #include "base/time/time.h"
+#include "base/trace_event/trace_event.h"
 #include "base/values.h"
 #include "net/base/address_family.h"
 #include "net/base/address_list.h"
 #include "net/base/host_port_pair.h"
 #include "net/base/ip_address.h"
 #include "net/base/ip_endpoint.h"
 #include "net/base/net_errors.h"
 #include "net/base/url_util.h"
 #include "net/dns/address_sorter.h"
 #include "net/dns/dns_client.h"
@@ skipping 709 matching lines @@
     params_.unresponsive_delay *= params_.retry_factor;
     StartLookupAttempt();
   }
 
   // Callback for when DoLookup() completes (runs on task runner thread).
   void OnLookupComplete(const AddressList& results,
                         const base::TimeTicks& start_time,
                         const uint32_t attempt_number,
                         int error,
                         const int os_error) {
+    TRACE_EVENT0("net", "net::ProcTask::OnLookupComplete");
     DCHECK(task_runner_->BelongsToCurrentThread());
     // If results are empty, we should return an error.
     bool empty_list_on_ok = (error == OK && results.empty());
     UMA_HISTOGRAM_BOOLEAN("DNS.EmptyAddressListAndNoError", empty_list_on_ok);
     if (empty_list_on_ok)
       error = ERR_NAME_NOT_RESOLVED;
 
     bool was_retry_attempt = attempt_number > 1;
 
     // Ideally the following code would be part of host_resolver_proc.cc,
@@ skipping 1665 matching lines @@
     dns_client_->SetConfig(dns_config);
     num_dns_failures_ = 0;
     if (dns_client_->GetConfig())
       UMA_HISTOGRAM_BOOLEAN("AsyncDNS.DnsClientEnabled", true);
   }
 
   AbortDnsTasks();
 }
 
 }  // namespace net