Instantiate ScopedTaskEnvironment in net unittests.

net/test/net_test_suite.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/test/net_test_suite.h"
 
-#include "base/message_loop/message_loop.h"
+#include "base/memory/ptr_util.h"
+#include "base/test/scoped_task_environment.h"
 #include "net/base/network_change_notifier.h"
 #include "net/http/http_stream_factory.h"
 #include "net/spdy/chromium/spdy_session.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 #if defined(USE_NSS_CERTS)
 #include "net/cert_net/nss_ocsp.h"
 #endif
 
 NetTestSuite::NetTestSuite(int argc, char** argv)
     : TestSuite(argc, argv) {
 }
 
 NetTestSuite::~NetTestSuite() {}
 
 void NetTestSuite::Initialize() {
   TestSuite::Initialize();
   InitializeTestThread();
 }
 
 void NetTestSuite::Shutdown() {
 #if defined(USE_NSS_CERTS)
   net::ShutdownNSSHttpIO();
 #endif
 
   // We want to destroy this here before the TestSuite continues to tear down
   // the environment.
-  message_loop_.reset();
+  scoped_task_environment_.reset();
 
   TestSuite::Shutdown();
 }
 
 void NetTestSuite::InitializeTestThread() {
   network_change_notifier_.reset(net::NetworkChangeNotifier::CreateMock());
 
   InitializeTestThreadNoNetworkChangeNotifier();
 }
 
 void NetTestSuite::InitializeTestThreadNoNetworkChangeNotifier() {
   host_resolver_proc_ = new net::RuleBasedHostResolverProc(NULL);
   scoped_host_resolver_proc_.Init(host_resolver_proc_.get());
   // In case any attempts are made to resolve host names, force them all to
   // be mapped to localhost.  This prevents DNS queries from being sent in
   // the process of running these unit tests.
   host_resolver_proc_->AddRule("*", "127.0.0.1");
 
-  message_loop_.reset(new base::MessageLoopForIO());
+  scoped_task_environment_ =
+      base::MakeUnique<base::test::ScopedTaskEnvironment>(
+          base::test::ScopedTaskEnvironment::MainThreadType::IO);
 }