[sync] Componentize sync: Part 2: Add SYNC_EXPORTs to files in src/sync/

sync/syncable/write_transaction.h

-// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Copyright 2012 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 SYNC_SYNCABLE_WRITE_TRANSACTION_H_
 #define SYNC_SYNCABLE_WRITE_TRANSACTION_H_
 
+#include "sync/base/sync_export.h"
 #include "sync/syncable/base_transaction.h"
 #include "sync/syncable/entry_kernel.h"
 
 namespace syncer {
 namespace syncable {
 
-extern const int64 kInvalidTransactionVersion;
+SYNC_EXPORT extern const int64 kInvalidTransactionVersion;
 
 // Locks db in constructor, unlocks in destructor.
 class WriteTransaction : public BaseTransaction {
  public:
   WriteTransaction(const tracked_objects::Location& from_here,
                    WriterTag writer, Directory* directory);
 
   // Constructor used for getting back transaction version after making sync
   // API changes to one model. If model is changed by the transaction,
   // the new transaction version of the model and modified nodes will be saved
@@ skipping 33 matching lines @@
   // indeed changed. kInvalidTransactionVersion otherwise. Not owned.
   int64* transaction_version_;
 
   DISALLOW_COPY_AND_ASSIGN(WriteTransaction);
 };
 
 }  // namespace syncable
 }  // namespace syncer
 
 #endif //  SYNC_SYNCABLE_WRITE_TRANSACTION_H_