Move the Mac Task Manager to the new backend code.

chrome/browser/task_manager/background_information.h

-// Copyright 2014 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_TASK_MANAGER_BACKGROUND_INFORMATION_H_
-#define CHROME_BROWSER_TASK_MANAGER_BACKGROUND_INFORMATION_H_
-
-#include "base/macros.h"
-#include "chrome/browser/task_manager/web_contents_information.h"
-
-namespace task_manager {
-
-// WebContentsInformation for BackgroundContents-owned WebContentses.
-class BackgroundInformation
-    : public NotificationObservingWebContentsInformation {
- public:
-  BackgroundInformation();
-  ~BackgroundInformation() override;
-
-  // WebContentsInformation implementation.
-  bool CheckOwnership(content::WebContents* web_contents) override;
-  void GetAll(const NewWebContentsCallback& callback) override;
-  std::unique_ptr<RendererResource> MakeResource(
-      content::WebContents* web_contents) override;
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(BackgroundInformation);
-};
-
-}  // namespace task_manager
-
-#endif  // CHROME_BROWSER_TASK_MANAGER_BACKGROUND_INFORMATION_H_