Followup to https://codereview.chromium.org/2902753003/

base/task_scheduler/environment_config.h

 // Copyright 2017 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_ENVIRONMENT_CONFIG_H_
 #define BASE_TASK_SCHEDULER_ENVIRONMENT_CONFIG_H_
 
 #include <stddef.h>
 
+#include "base/base_export.h"
 #include "base/task_scheduler/task_traits.h"
 #include "base/threading/thread.h"
 
 namespace base {
 namespace internal {
 
 enum EnvironmentType {
   BACKGROUND = 0,
   BACKGROUND_BLOCKING,
   FOREGROUND,
@@ skipping 16 matching lines @@
     {"Foreground", base::ThreadPriority::NORMAL},
     {"ForegroundBlocking", base::ThreadPriority::NORMAL},
 };
 
 size_t BASE_EXPORT GetEnvironmentIndexForTraits(const TaskTraits& traits);
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // BASE_TASK_SCHEDULER_ENVIRONMENT_CONFIG_H_