Add constexpr TaskTraits constructor.

base/task_scheduler/task_traits.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_traits.h"
 
 #include <stddef.h>
 
 #include <ostream>
 
 #include "base/logging.h"
 
 namespace base {
 
-TaskTraits::TaskTraits() = default;
-TaskTraits::~TaskTraits() = default;
-
 TaskTraits& TaskTraits::MayBlock() {
   may_block_ = true;
   return *this;
 }
 
 TaskTraits& TaskTraits::WithBaseSyncPrimitives() {
   with_base_sync_primitives_ = true;
   return *this;
 }
 
@@ skipping 41 matching lines @@
   return os;
 }
 
 std::ostream& operator<<(std::ostream& os,
                          const TaskShutdownBehavior& shutdown_behavior) {
   os << TaskShutdownBehaviorToString(shutdown_behavior);
   return os;
 }
 
 }  // namespace base