Remove the file thread dependency from FileNetLogObserver.

components/net_log/net_export_file_writer.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 <set>
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 166 matching lines @@
     log_path_ = log_path;
 
   DCHECK(!log_path_.empty());
 
   state_ = STATE_STARTING_LOG;
 
   NotifyStateObserversAsync();
 
   std::unique_ptr<base::Value> constants(
       ChromeNetLog::GetConstants(command_line_string, channel_string));
-  // Instantiate a FileNetLogObserver in unbounded mode.
-  file_net_log_observer_ = net::FileNetLogObserver::CreateUnbounded(
-      file_task_runner_, log_path_, std::move(constants));
+
+  file_net_log_observer_ =
+      net::FileNetLogObserver::CreateUnbounded(log_path_, std::move(constants));
 
   net_task_runner_->PostTaskAndReply(
       FROM_HERE,
       base::Bind(&CreateNetLogEntriesForActiveObjects, context_getters,
                  base::Unretained(file_net_log_observer_.get())),
       base::Bind(
           &NetExportFileWriter::StartNetLogAfterCreateEntriesForActiveObjects,
           weak_ptr_factory_.GetWeakPtr(), capture_mode));
 }
 
@@ skipping 168 matching lines @@
 
 void NetExportFileWriter::ResetObserverThenSetStateNotLogging() {
   DCHECK(thread_checker_.CalledOnValidThread());
   file_net_log_observer_.reset();
   state_ = STATE_NOT_LOGGING;
 
   NotifyStateObservers();
 }
 
 }  // namespace net_log