Do not inherit TaskPriority in TaskTraits.

base/task_scheduler/task.cc

Index: base/task_scheduler/task.cc
diff --git a/base/task_scheduler/task.cc b/base/task_scheduler/task.cc
index fc513e3e9fb53945bc22b21185430457e9e382ea..9bd99789cc34a7af2143907c17387b9720a68432 100644
--- a/base/task_scheduler/task.cc
+++ b/base/task_scheduler/task.cc
@@ -7,6 +7,7 @@
 #include <utility>
 
 #include "base/critical_closure.h"
+#include "base/logging.h"
 
 namespace base {
 namespace internal {
@@ -29,7 +30,10 @@ Task::Task(const tracked_objects::Location& posted_from,
                  ? 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;