[Sync] Convert sync to a static library.

components/sync/core/shutdown_reason.h

 // Copyright 2014 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 COMPONENTS_SYNC_CORE_SHUTDOWN_REASON_H_
 #define COMPONENTS_SYNC_CORE_SHUTDOWN_REASON_H_
 
-#include "components/sync/base/sync_export.h"
-
 namespace syncer {
 
 // Reason for shutting down sync engine.
 enum ShutdownReason {
   STOP_SYNC,         // Sync is asked to stop, e.g. due to scarce resource.
   DISABLE_SYNC,      // Sync is disabled, e.g. user sign out, dashboard clear.
   BROWSER_SHUTDOWN,  // Browser is closed.
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_CORE_SHUTDOWN_REASON_H_