TaskScheduler: Initialize TaskTraits with the priority of the current thread.

base/task_scheduler/task_traits.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_TASK_TRAITS_H_
 #define BASE_TASK_SCHEDULER_TASK_TRAITS_H_
 
 #include <stdint.h>
 
 #include <iosfwd>
@@ skipping 62 matching lines @@
   // Note: Tasks with BACKGROUND priority that block shutdown will be promoted
   // to USER_VISIBLE priority during shutdown.
   BLOCK_SHUTDOWN,
 };
 
 // Describes metadata for a single task or a group of tasks.
 class BASE_EXPORT TaskTraits {
  public:
   // Constructs a default TaskTraits for tasks with
   //     (1) no I/O,
-  //     (2) low priority, and
+  //     (2) priority inherited from the calling context, and
   //     (3) may block shutdown or be skipped on shutdown.
-  // Tasks that require stricter guarantees should highlight those by requesting
+  // Tasks that require stricter guarantees and/or know the specific
+  // TaskPriority appropriate for them should highlight those by requesting
   // explicit traits below.
   TaskTraits();
   TaskTraits(const TaskTraits& other) = default;
   TaskTraits& operator=(const TaskTraits& other) = default;
   ~TaskTraits();
 
   // Allows tasks with these traits to wait on synchronous file I/O.
   TaskTraits& WithFileIO();
 
   // Allows tasks with these traits to wait on things other than file I/O. In
@@ skipping 38 matching lines @@
 // DCHECK and EXPECT statements.
 BASE_EXPORT std::ostream& operator<<(std::ostream& os,
                                      const TaskPriority& shutdown_behavior);
 BASE_EXPORT std::ostream& operator<<(
     std::ostream& os,
     const TaskShutdownBehavior& shutdown_behavior);
 
 }  // namespace base
 
 #endif  // BASE_TASK_SCHEDULER_TASK_TRAITS_H_