[sync] Componentize sync: Part 6: Add more SYNC_EXPORTs to files in src/sync/

sync/js/js_backend.h

Index: sync/js/js_backend.h
diff --git a/sync/js/js_backend.h b/sync/js/js_backend.h
index ea1d7aa08ec1897aab156ea7709a84d889fa264c..e39600a8bcb9750f82fb51e96039379e233938d0 100644
--- a/sync/js/js_backend.h
+++ b/sync/js/js_backend.h
@@ -1,4 +1,4 @@
-// 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.
 
@@ -9,6 +9,8 @@
 
 #include <string>
 
+#include "sync/base/sync_export.h"
+
 namespace syncer {
 
 class JsArgList;
@@ -19,7 +21,7 @@ template <typename T> class WeakHandle;
 // Interface representing the backend of chrome://sync-internals.  A
 // JsBackend can handle messages and can emit events to a
 // JsEventHandler.
-class JsBackend {
+class SYNC_EXPORT_PRIVATE JsBackend {
  public:
   // Starts emitting events to the given handler, if initialized.
   virtual void SetJsEventHandler(