Encouraging ThreadTaskRunnerHandle usage in net/dns module

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"
 
 #if defined(OS_WIN)
 #include <Winsock2.h>
 #elif defined(OS_POSIX)
 #include <netdb.h>
 #endif
 
 #include <cmath>
 #include <utility>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/callback.h"
 #include "base/compiler_specific.h"
 #include "base/debug/debugger.h"
 #include "base/debug/stack_trace.h"
-#include "base/message_loop/message_loop_proxy.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/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/values.h"
 #include "net/base/address_family.h"
 #include "net/base/address_list.h"
 #include "net/base/dns_reloader.h"
 #include "net/base/dns_util.h"
 #include "net/base/host_port_pair.h"
 #include "net/base/ip_endpoint.h"
 #include "net/base/net_errors.h"
@@ skipping 525 matching lines @@
   typedef base::Callback<void(int net_error,
                               const AddressList& addr_list)> Callback;
 
   ProcTask(const Key& key,
            const ProcTaskParams& params,
            const Callback& callback,
            const BoundNetLog& job_net_log)
       : key_(key),
         params_(params),
         callback_(callback),
-        origin_loop_(base::MessageLoopProxy::current()),
+        origin_loop_(base::ThreadTaskRunnerHandle::Get()),
         attempt_number_(0),
         completed_attempt_number_(0),
         completed_attempt_error_(ERR_UNEXPECTED),
         had_non_speculative_request_(false),
         net_log_(job_net_log) {
     if (!params_.resolver_proc.get())
       params_.resolver_proc = HostResolverProc::GetDefault();
     // If default is unset, use the system proc.
     if (!params_.resolver_proc.get())
       params_.resolver_proc = new SystemHostResolverProc();
@@ skipping 310 matching lines @@
   // Holds an owning reference to the HostResolverProc that we are going to use.
   // This may not be the current resolver procedure by the time we call
   // ResolveAddrInfo, but that's OK... we'll use it anyways, and the owning
   // reference ensures that it remains valid until we are done.
   ProcTaskParams params_;
 
   // The listener to the results of this ProcTask.
   Callback callback_;
 
   // Used to post ourselves onto the origin thread.
-  scoped_refptr<base::MessageLoopProxy> origin_loop_;
+  scoped_refptr<base::SingleThreadTaskRunner> origin_loop_;

[asanka, 2015/05/14 04:06:36]

Could you rename this to task_runner_ and document it as the task runner for the
origin thread?

[anujsharma, 2015/05/14 04:39:40]

Done.

 
   // Keeps track of the number of attempts we have made so far to resolve the
   // host. Whenever we start an attempt to resolve the host, we increase this
   // number.
   uint32 attempt_number_;
 
   // The index of the attempt which finished first (or 0 if the job is still in
   // progress).
   uint32 completed_attempt_number_;
 
@@ skipping 1474 matching lines @@
     dns_client_->SetConfig(dns_config);
     num_dns_failures_ = 0;
     if (dns_client_->GetConfig())
       UMA_HISTOGRAM_BOOLEAN("AsyncDNS.DnsClientEnabled", true);
   }
 
   AbortDnsTasks();
 }
 
 }  // namespace net