Do not inherit TaskPriority in TaskTraits.

base/task_scheduler/sequence.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/sequence.h"
 
 #include <utility>
 
 #include "base/logging.h"
 #include "base/time/time.h"
 
 namespace base {
 namespace internal {
 
 Sequence::Sequence() = default;
 
 bool Sequence::PushTask(std::unique_ptr<Task> task) {
   DCHECK(task);
+  DCHECK_LT(static_cast<size_t>(task->traits.priority()),
+            arraysize(num_tasks_per_priority_));
 
   // Use CHECK instead of DCHECK to crash earlier. See http://crbug.com/711167
   // for details.
   CHECK(task->task);
   DCHECK(task->sequenced_time.is_null());
   task->sequenced_time = base::TimeTicks::Now();
 
   AutoSchedulerLock auto_lock(lock_);
   ++num_tasks_per_priority_[static_cast<int>(task->traits.priority())];
   queue_.push(std::move(task));
@@ skipping 52 matching lines @@
     next_task_sequenced_time = queue_.front()->sequenced_time;
   }
 
   return SequenceSortKey(priority, next_task_sequenced_time);
 }
 
 Sequence::~Sequence() = default;
 
 }  // namespace internal
 }  // namespace base