chromium - WeakPtrFactory members which refer to their outer class must be the last member in the ou

前言

做实验，想向chromium工程的类中加入一个成员变量，结果出现如下编译错误：

WeakPtrFactory members which refer to their outer class must be the last member in the outer class definition

没想到是啥错误，其实错误提示也很明显。
后来看看类有没有WeakPtrFactory类型的成员变量，真有啊，将自己定义的新变量，放在他上面就行。说明，如果类中有WeakPtrFactory类型的成员变量，必须是类中最后一个成员变量. autoninja检查的挺严格的。

实验

// Copyright 2017 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.

#ifndef CHROME_BROWSER_UI_WEBUI_DOWNLOAD_INTERNALS_DOWNLOAD_INTERNALS_UI_MESSAGE_HANDLER_H_
#define CHROME_BROWSER_UI_WEBUI_DOWNLOAD_INTERNALS_DOWNLOAD_INTERNALS_UI_MESSAGE_HANDLER_H_

#include <string>
#include "base/macros.h"
#include "base/memory/weak_ptr.h"
#include "components/download/public/background_service/logger.h"
#include "content/public/browser/web_ui_message_handler.h"

// Z:\chromium\src\url\gurl.h
#include "url/gurl.h"

namespace download {
class DownloadService;
}

namespace download_internals {

// Class acting as a controller of the chrome://download-internals WebUI.
class DownloadInternalsUIMessageHandler : public content::WebUIMessageHandler,
                                          public download::Logger::Observer {
 public:
  DownloadInternalsUIMessageHandler();
  ~DownloadInternalsUIMessageHandler() override;

  // content::WebUIMessageHandler implementation.
  void RegisterMessages() override;

  // download::Logger::Observer implementation.
  void OnServiceStatusChanged(const base::Value& service_status) override;
  void OnServiceDownloadsAvailable(
      const base::Value& service_downloads) override;
  void OnServiceDownloadChanged(const base::Value& service_download) override;
  void OnServiceDownloadFailed(const base::Value& service_download) override;
  void OnServiceRequestMade(const base::Value& service_request) override;

 private:
  // Get the current DownloadService and sub component statuses.
  void HandleGetServiceStatus(const base::ListValue* args);
  void HandleGetServiceDownloads(const base::ListValue* args);

  // Starts a background download.
  void HandleStartDownload(const base::ListValue* args);
	void HandleStartDownload_url(GURL& url);

	bool get_string_value_by_key_from_value(const base::Value& value, const char* psz_key, std::string& str_value);
	bool get_double_value_by_key_from_value(const base::Value& value, const char* psz_key, double& f_value);

private:
  download::DownloadService* download_service_;

	// base::WeakPtrFactory<>类型的成员变量必须是本类的最后一个成员变量
	// 成员变量如果是类, 必须加在base::WeakPtrFactory类型成员变量的上面，否则报错如下
	// WeakPtrFactory members which refer to their outer class must be the last member in the outer class definition
	std::string m_str_url_by_js_first; // 保存第一次js发来的url

	base::WeakPtrFactory<DownloadInternalsUIMessageHandler> weak_ptr_factory_;

	DISALLOW_COPY_AND_ASSIGN(DownloadInternalsUIMessageHandler);
};

}  // namespace download_internals

#endif  // CHROME_BROWSER_UI_WEBUI_DOWNLOAD_INTERNALS_DOWNLOAD_INTERNALS_UI_MESSAGE_HANDLER_H_