TaskScheduler: Add internal::GetTaskPriorityForCurrentThread().

base/task_scheduler/task_priority_for_current_thread.h

Index: base/task_scheduler/task_priority_for_current_thread.h
diff --git a/base/task_scheduler/task_priority_for_current_thread.h b/base/task_scheduler/task_priority_for_current_thread.h
new file mode 100644
index 0000000000000000000000000000000000000000..8eb728f458682ff15aa6d810c7274e506d877b4b
--- /dev/null
+++ b/base/task_scheduler/task_priority_for_current_thread.h
@@ -0,0 +1,36 @@
+// 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_PRIORITY_FOR_CURRENT_THREAD_H_
+#define BASE_TASK_SCHEDULER_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 {

[robliao, 2016/12/01 19:27:27]

The file name should match the class.
scoped_set_task_priority_for_current_thread.[cc|h]
That's a mouthful!

[fdoray, 2016/12/01 19:41:07]

Even if this file also declares a GetTaskPriorityForCurrentThread() function? 

[robliao, 2016/12/01 20:08:57]

That's the convention we've used so far. It goes with the predominant class. 
https://codereview.chromium.org/1908633002/diff/40001/base/test/command_line_...

https://google.github.io/styleguide/cppguide.html#File_Names (on convention)

https://cs.chromium.org/chromium/src/base/sequence_token.h defines SequenceToken
as the predominant class. TaskToken and ScopedSetSequenceTokenForCurrentThread
simply jump along for the ride. Arguably they should be in different files.

[fdoray, 2016/12/01 20:23:36]

Done.

+ 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_TASK_PRIORITY_FOR_CURRENT_THREAD_H_