Revert of Add ScopedTaskEnvironment::ExecutionControlMode.

base/task_scheduler/task_tracker_posix.h

 // Copyright 2016 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 BASE_TASK_SCHEDULER_TASK_TRACKER_POSIX_H_
 #define BASE_TASK_SCHEDULER_TASK_TRACKER_POSIX_H_
 
 #include <memory>
 
 #include "base/base_export.h"
@@ skipping 32 matching lines @@
   // TODO(robliao): http://crbug.com/698140. This addresses service thread tasks
   // that could run after the task scheduler has shut down. Anything from the
   // service thread is exempted from the task scheduler shutdown DCHECKs.
   void set_service_thread_handle(
       const PlatformThreadHandle& service_thread_handle) {
     DCHECK(!service_thread_handle.is_null());
     service_thread_handle_ = service_thread_handle;
   }
 #endif
 
- protected:
+ private:
   // TaskTracker:
   void PerformRunTask(std::unique_ptr<Task> task,
                       const SequenceToken& sequence_token) override;
 
- private:
 #if DCHECK_IS_ON()
   bool IsPostingBlockShutdownTaskAfterShutdownAllowed() override;
 #endif
 
   MessageLoopForIO* watch_file_descriptor_message_loop_ = nullptr;
 
 #if DCHECK_IS_ON()
   PlatformThreadHandle service_thread_handle_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(TaskTrackerPosix);
 };
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // BASE_TASK_SCHEDULER_TASK_TRACKER_POSIX_H_