[Sync] Convert sync to a static library.

components/sync/js/js_backend.h

 // 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 COMPONENTS_SYNC_JS_JS_BACKEND_H_
 #define COMPONENTS_SYNC_JS_JS_BACKEND_H_
 
 // See README.js for design comments.
 
 #include <string>
 
-#include "components/sync/base/sync_export.h"
-
 namespace syncer {
 
 class JsEventHandler;
 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 SYNC_EXPORT JsBackend {
+class JsBackend {
  public:
   // Starts emitting events to the given handler, if initialized.
   virtual void SetJsEventHandler(
       const WeakHandle<JsEventHandler>& event_handler) = 0;
 
  protected:
   virtual ~JsBackend() {}
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_JS_JS_BACKEND_H_