[Part 1 of 6] Move MockWebContentsTaskManager into its own file.

chrome/browser/task_management/task_management_browsertest_util.h

-// 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.
-
-#ifndef CHROME_BROWSER_TASK_MANAGEMENT_TASK_MANAGEMENT_BROWSERTEST_UTIL_H_
-#define CHROME_BROWSER_TASK_MANAGEMENT_TASK_MANAGEMENT_BROWSERTEST_UTIL_H_
-
-#include "base/macros.h"
-#include "chrome/browser/task_management/providers/task_provider_observer.h"
-#include "chrome/browser/task_management/providers/web_contents/web_contents_tags_manager.h"
-#include "chrome/browser/task_management/providers/web_contents/web_contents_task_provider.h"
-
-namespace task_management {
-
-// Defines a test class that will act as a task manager that is designed to
-// only observe the WebContents-based tasks.
-class MockWebContentsTaskManager : public TaskProviderObserver {
- public:
-  MockWebContentsTaskManager();
-  ~MockWebContentsTaskManager() override;
-
-  // task_management::TaskProviderObserver:
-  void TaskAdded(Task* task) override;
-  void TaskRemoved(Task* task) override;
-
-  // Start / Stop observing the WebContentsTaskProvider.
-  void StartObserving();
-  void StopObserving();
-
-  const std::vector<Task*>& tasks() const { return tasks_; }
-
- private:
-  std::vector<Task*> tasks_;
-  WebContentsTaskProvider provider_;
-
-  DISALLOW_COPY_AND_ASSIGN(MockWebContentsTaskManager);
-};
-
-}  // namespace task_management
-
-#endif  // CHROME_BROWSER_TASK_MANAGEMENT_TASK_MANAGEMENT_BROWSERTEST_UTIL_H_