TaskScheduler: Add internal::GetTaskPriorityForCurrentThread().

base/task_scheduler/scoped_set_task_priority_for_current_thread.cc

Index: base/task_scheduler/scoped_set_task_priority_for_current_thread.cc
diff --git a/base/task_scheduler/scoped_set_task_priority_for_current_thread.cc b/base/task_scheduler/scoped_set_task_priority_for_current_thread.cc
new file mode 100644
index 0000000000000000000000000000000000000000..a163863d0ff833a2aabf3eee158abb2b093548fa
--- /dev/null
+++ b/base/task_scheduler/scoped_set_task_priority_for_current_thread.cc
@@ -0,0 +1,41 @@
+// 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/lazy_instance.h"
+#include "base/logging.h"
+#include "base/threading/thread_local.h"
+
+namespace base {
+namespace internal {
+
+namespace {
+
+LazyInstance<ThreadLocalPointer<const TaskPriority>>::Leaky
+    tls_task_priority_for_current_thread = LAZY_INSTANCE_INITIALIZER;
+
+}  // namespace
+
+ScopedSetTaskPriorityForCurrentThread::ScopedSetTaskPriorityForCurrentThread(
+    TaskPriority priority)
+    : priority_(priority) {
+  DCHECK(!tls_task_priority_for_current_thread.Get().Get());
+  tls_task_priority_for_current_thread.Get().Set(&priority_);
+}
+
+ScopedSetTaskPriorityForCurrentThread::
+    ~ScopedSetTaskPriorityForCurrentThread() {
+  DCHECK_EQ(&priority_, tls_task_priority_for_current_thread.Get().Get());
+  tls_task_priority_for_current_thread.Get().Set(nullptr);
+}
+
+TaskPriority GetTaskPriorityForCurrentThread() {
+  const TaskPriority* priority =
+      tls_task_priority_for_current_thread.Get().Get();
+  return priority ? *priority : TaskPriority::USER_VISIBLE;
+}
+
+}  // namespace internal
+}  // namespace base