Revert of scheduler: Always create a real scheduler in unit tests

components/scheduler/test/lazy_scheduler_message_loop_delegate_for_tests.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 COMPONENTS_SCHEDULER_TEST_LAZY_SCHEDULER_MESSAGE_LOOP_DELEGATE_FOR_TESTS_H_
-#define COMPONENTS_SCHEDULER_TEST_LAZY_SCHEDULER_MESSAGE_LOOP_DELEGATE_FOR_TESTS_H_
-
-#include "base/message_loop/message_loop.h"
-#include "components/scheduler/child/nestable_single_thread_task_runner.h"
-
-namespace scheduler {
-
-// This class connects the scheduler to a MessageLoop, but unlike
-// SchedulerMessageLoopDelegate it allows the message loop to be created lazily
-// after the scheduler has been brought up. This is needed in testing scenarios
-// where Blink is initialized before a MessageLoop has been created.
-//
-// TODO(skyostil): Fix the relevant test suites and remove this class
-// (crbug.com/495659).
-class LazySchedulerMessageLoopDelegateForTests
-    : public NestableSingleThreadTaskRunner {
- public:
-  static scoped_refptr<LazySchedulerMessageLoopDelegateForTests> Create();
-
-  // NestableSingleThreadTaskRunner implementation
-  bool PostDelayedTask(const tracked_objects::Location& from_here,
-                       const base::Closure& task,
-                       base::TimeDelta delay) override;
-  bool PostNonNestableDelayedTask(const tracked_objects::Location& from_here,
-                                  const base::Closure& task,
-                                  base::TimeDelta delay) override;
-  bool RunsTasksOnCurrentThread() const override;
-  bool IsNested() const override;
-  void AddTaskObserver(base::MessageLoop::TaskObserver* task_observer) override;
-  void RemoveTaskObserver(
-      base::MessageLoop::TaskObserver* task_observer) override;
-
- private:
-  LazySchedulerMessageLoopDelegateForTests();
-  ~LazySchedulerMessageLoopDelegateForTests() override;
-
-  bool HasMessageLoop() const;
-  base::MessageLoop* EnsureMessageLoop() const;
-
-  base::PlatformThreadId thread_id_;
-  // Task observers which have not yet been registered to a message loop. Not
-  // owned.
-  mutable base::hash_set<base::MessageLoop::TaskObserver*> pending_observers_;
-
-  DISALLOW_COPY_AND_ASSIGN(LazySchedulerMessageLoopDelegateForTests);
-};
-
-}  // namespace scheduler
-
-#endif  // COMPONENTS_SCHEDULER_TEST_LAZY_SCHEDULER_MESSAGE_LOOP_DELEGATE_FOR_TESTS_H_