TaskScheduler: Add internal::GetTaskPriorityForCurrentThread().

base/task_scheduler/task_traits_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_CURRENT_TASK_TRAITS_H_
+#define BASE_TASK_SCHEDULER_CURRENT_TASK_TRAITS_H_
+
+#include "base/base_export.h"
+#include "base/logging.h"
+#include "base/macros.h"
+
+namespace base {
+
+class TaskTraits;
+
+namespace internal {
+
+class BASE_EXPORT ScopedSetTaskTraitsForCurrentThread {
+ public:
+  // Within the scope of this object, GetTaskTraitsForCurrentThread() will
+  // return |traits|.
+  ScopedSetTaskTraitsForCurrentThread(const TaskTraits* traits);
+  ~ScopedSetTaskTraitsForCurrentThread();
+
+ private:
+#if DCHECK_IS_ON()
+  const TaskTraits* const traits_;
+#endif
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedSetTaskTraitsForCurrentThread);
+};
+
+// Returns the TaskTraits of the task running on the current thread.
+BASE_EXPORT const TaskTraits* GetTaskTraitsForCurrentThread();
+
+}  // namespace internal
+}  // namespace base
+
+#endif  // BASE_TASK_SCHEDULER_CURRENT_TASK_TRAITS_H_