TaskScheduler: Add internal::GetTaskPriorityForCurrentThread().

base/task_scheduler/scoped_set_task_priority_for_current_thread_unittest.cc

+// 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.
+
+#include "base/task_scheduler/scoped_set_task_priority_for_current_thread.h"
+
+#include "base/task_scheduler/task_traits.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace base {
+namespace internal {
+
+TEST(TaskSchedulerScopedSetTaskPriorityForCurrentThreadTest,
+     ScopedSetTaskPriorityForCurrentThread) {
+  EXPECT_EQ(TaskPriority::USER_VISIBLE, GetTaskPriorityForCurrentThread());
+  {
+    ScopedSetTaskPriorityForCurrentThread
+        scoped_set_task_priority_for_current_thread(
+            TaskPriority::USER_BLOCKING);
+    EXPECT_EQ(TaskPriority::USER_BLOCKING, GetTaskPriorityForCurrentThread());
+  }
+  EXPECT_EQ(TaskPriority::USER_VISIBLE, GetTaskPriorityForCurrentThread());
+}
+
+}  // namespace internal
+}  // namespace base