[Sync] Convert sync to a static library.

components/sync/syncable/syncable_base_write_transaction.h

 // Copyright 2013 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_SYNCABLE_SYNCABLE_BASE_WRITE_TRANSACTION_H_
 #define COMPONENTS_SYNC_SYNCABLE_SYNCABLE_BASE_WRITE_TRANSACTION_H_
 
 #include "base/macros.h"
-#include "components/sync/base/sync_export.h"
 #include "components/sync/syncable/syncable_base_transaction.h"
 
 namespace syncer {
 namespace syncable {
 
 // A base class shared by both ModelNeutralWriteTransaction and
 // WriteTransaction.
-class SYNC_EXPORT BaseWriteTransaction : public BaseTransaction {
+class BaseWriteTransaction : public BaseTransaction {
  public:
   virtual void TrackChangesTo(const EntryKernel* entry) = 0;
 
  protected:
   BaseWriteTransaction(const tracked_objects::Location location,
                        const char* name,
                        WriterTag writer,
                        Directory* directory);
   ~BaseWriteTransaction() override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(BaseWriteTransaction);
 };
 
 }  // namespace syncable
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_SYNCABLE_SYNCABLE_BASE_WRITE_TRANSACTION_H_