TaskScheduler: Add internal::GetTaskPriorityForCurrentThread().

base/task_scheduler/scoped_set_task_priority_for_current_thread.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_SCOPED_SET_TASK_PRIORITY_FOR_CURRENT_THREAD_H_
+#define BASE_TASK_SCHEDULER_SCOPED_SET_TASK_PRIORITY_FOR_CURRENT_THREAD_H_
+
+#include "base/base_export.h"
+#include "base/macros.h"
+#include "base/task_scheduler/task_traits.h"
+
+namespace base {
+namespace internal {
+
+class BASE_EXPORT ScopedSetTaskPriorityForCurrentThread {
+ public:
+  // Within the scope of this object, GetTaskPriorityForCurrentThread() will
+  // return |priority|.
+  ScopedSetTaskPriorityForCurrentThread(TaskPriority priority);
+  ~ScopedSetTaskPriorityForCurrentThread();
+
+ private:
+  const TaskPriority priority_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedSetTaskPriorityForCurrentThread);
+};
+
+// Returns the priority of the TaskScheduler task running on the current thread,
+// or TaskPriority::USER_VISIBLE if no TaskScheduler task is running on the
+// current thread.
+BASE_EXPORT TaskPriority GetTaskPriorityForCurrentThread();
+
+}  // namespace internal
+}  // namespace base
+
+#endif  // BASE_TASK_SCHEDULER_SCOPED_SET_TASK_PRIORITY_FOR_CURRENT_THREAD_H_