Do not inherit TaskPriority in TaskTraits.

base/task_scheduler/task.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/task.h"
 
 #include <utility>
 
 #include "base/critical_closure.h"
+#include "base/logging.h"
 
 namespace base {
 namespace internal {
 
 Task::Task(const tracked_objects::Location& posted_from,
            OnceClosure task,
            const TaskTraits& traits,
            TimeDelta delay)
     : PendingTask(
           posted_from,
           traits.shutdown_behavior() == TaskShutdownBehavior::BLOCK_SHUTDOWN
               ? MakeCriticalClosure(std::move(task))
               : std::move(task),
           delay.is_zero() ? TimeTicks() : TimeTicks::Now() + delay,
           false),  // Not nestable.
       // Prevent a delayed BLOCK_SHUTDOWN task from blocking shutdown before
       // being scheduled by changing its shutdown behavior to SKIP_ON_SHUTDOWN.
       traits(!delay.is_zero() && traits.shutdown_behavior() ==
                                      TaskShutdownBehavior::BLOCK_SHUTDOWN
                  ? TaskTraits(traits).WithShutdownBehavior(
                        TaskShutdownBehavior::SKIP_ON_SHUTDOWN)
                  : traits),
-      delay(delay) {}
+      delay(delay) {
+  DCHECK_LE(static_cast<int>(traits.priority()),
+            static_cast<int>(TaskPriority::HIGHEST));
+}
 
 Task::~Task() = default;
 
 }  // namespace internal
 }  // namespace base