[CrNet] Properly setup net log.

ios/crnet/crnet_net_log.cc

-// Copyright 2015 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 "ios/crnet/crnet_net_log.h"
-
-#include "base/files/file_path.h"
-#include "base/files/file_util.h"
-#include "base/files/scoped_file.h"
-#include "base/values.h"
-#include "net/log/net_log.h"
-#include "net/log/net_log_util.h"
-#include "net/log/write_to_file_net_log_observer.h"
-
-CrNetNetLog::CrNetNetLog() { }
-CrNetNetLog::~CrNetNetLog() { }
-
-bool CrNetNetLog::Start(const base::FilePath& log_file,
-                        CrNetNetLog::Mode mode) {
-  DCHECK(thread_checker_.CalledOnValidThread());
-  base::FilePath temp_dir;
-  if (!base::GetTempDir(&temp_dir))
-    return false;
-
-  base::FilePath full_path = temp_dir.Append(log_file);
-  base::ScopedFILE file(base::OpenFile(full_path, "w"));
-  if (!file)
-    return false;
-
-  scoped_ptr<base::Value> constants(net::GetNetConstants().Pass());
-
-  net::NetLogCaptureMode capture_mode = mode == LOG_ALL_BYTES ?
-      net::NetLogCaptureMode::IncludeSocketBytes() :
-      net::NetLogCaptureMode::Default();
-  write_to_file_observer_.reset(new net::WriteToFileNetLogObserver());
-  write_to_file_observer_->set_capture_mode(capture_mode);
-  write_to_file_observer_->StartObserving(this, file.Pass(), constants.get(),
-                                          nullptr);
-  return true;
-}
-
-void CrNetNetLog::Stop() {
-  DCHECK(thread_checker_.CalledOnValidThread());
-  write_to_file_observer_->StopObserving(nullptr);
-  write_to_file_observer_.reset();
-}