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

sync/syncable/write_transaction.h

Index: sync/syncable/write_transaction.h
diff --git a/sync/syncable/write_transaction.h b/sync/syncable/write_transaction.h
index 6a369638b65674983913f58b8b43456dd2959112..875f6ec0c7bdb24209aff0e093646f6f3712949c 100644
--- a/sync/syncable/write_transaction.h
+++ b/sync/syncable/write_transaction.h
@@ -1,17 +1,18 @@
-// 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 {