Remove the file thread dependency from FileNetLogObserver.

components/net_log/net_export_file_writer_unittest.cc

 // Copyright (c) 2013 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 "components/net_log/net_export_file_writer.h"
 
 #include <stdint.h>
 
 #include <memory>
 
 #include "base/command_line.h"
 #include "base/compiler_specific.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/files/scoped_file.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/json/json_reader.h"
 #include "base/json/json_string_value_serializer.h"
-#include "base/message_loop/message_loop.h"
-#include "base/run_loop.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/threading/thread.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/values.h"
 #include "build/build_config.h"
 #include "components/net_log/chrome_net_log.h"
 #include "net/base/test_completion_callback.h"
 #include "net/http/http_network_session.h"
 #include "net/log/net_log_capture_mode.h"
 #include "net/log/net_log_event_type.h"
 #include "net/traffic_annotation/network_traffic_annotation_test_helper.h"
@@ skipping 399 matching lines @@
 
   // The default log path that |file_writer_| will use is cached here.
   base::FilePath default_log_path_;
 
   base::Thread file_thread_;
   base::Thread net_thread_;
 
   TestStateObserver test_state_observer_;
 
  private:
-  // Allows tasks to be posted to the main thread.
-  base::MessageLoop message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
 };
 
 TEST_F(NetExportFileWriterTest, InitFail) {
   // Override file_writer_'s default log base directory getter to always
   // fail.
   file_writer_.SetDefaultLogBaseDirectoryGetterForTest(
       base::Bind([](base::FilePath* path) -> bool { return false; }));
 
   // Initialization should fail due to the override.
   ASSERT_TRUE(InitializeThenVerifyNewState(false, false));
@@ skipping 335 matching lines @@
   // StartNetLog() call (called by StartThenVerifyState()).
   std::unique_ptr<base::DictionaryValue> state =
       test_state_observer_.WaitForNewState();
   ASSERT_TRUE(VerifyState(std::move(state), kStateStoppingLogString));
   state = test_state_observer_.WaitForNewState();
   ASSERT_TRUE(VerifyState(std::move(state), kStateNotLoggingString, true, true,
                           kCaptureModeIncludeSocketBytesString));
 }
 
 }  // namespace net_log