Do not inherit TaskPriority in TaskTraits.

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 17 matching lines @@
   // Examples:
   // - Updating the UI to reflect progress on a long task.
   // - Loading data that might be shown in the UI after a future user
   //   interaction.
   USER_VISIBLE,
   // This task affects UI immediately after a user interaction.
   // Example: Generating data shown in the UI immediately after a click.
   USER_BLOCKING,
   // This will always be equal to the highest priority available.
   HIGHEST = USER_BLOCKING,
+  // Priority is inherited from the calling context.
+  INHERITED,
 };
 
 // Valid shutdown behaviors supported by the task scheduler.
 enum class TaskShutdownBehavior {
   // Tasks posted with this mode which have not started executing before
   // shutdown is initiated will never run. Tasks with this mode running at
   // shutdown will be ignored (the worker will not be joined).
   //
   // This option provides a nice way to post stuff you don't want blocking
   // shutdown. For example, you might be doing a slow DNS lookup and if it's
@@ skipping 117 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_