Enable component build for browser_context_keyed_service.

components/browser_context_keyed_service/browser_context_keyed_service.h

 // Copyright (c) 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_BROWSER_CONTEXT_KEYED_SERVICE_BROWSER_CONTEXT_KEYED_SERVICE_H_
 #define COMPONENTS_BROWSER_CONTEXT_KEYED_SERVICE_BROWSER_CONTEXT_KEYED_SERVICE_H_
 
+#include "components/browser_context_keyed_service/browser_context_keyed_service_export.h"
+
 class BrowserContextKeyedServiceFactory;
 
 // Base class for all BrowserContextKeyedServices to allow for correct
 // destruction order.
 //
 // Many services that hang off BrowserContext have a two-pass shutdown. Many
 // subsystems need a first pass shutdown phase where they drop references. Not
 // all services will need this, so there's a default implementation. Only once
 // every system has been given a chance to drop references do we start deleting
 // objects.
-class BrowserContextKeyedService {
+class BROWSER_CONTEXT_KEYED_SERVICE_EXPORT BrowserContextKeyedService {
  public:
   // The first pass is to call Shutdown on a BrowserContextKeyedService.
   virtual void Shutdown() {}
 
  protected:
   friend class BrowserContextKeyedServiceFactory;
 
   // The second pass is the actual deletion of each object.
   virtual ~BrowserContextKeyedService() {}
 };
 
 #endif  // COMPONENTS_BROWSER_CONTEXT_KEYED_SERVICE_BROWSER_CONTEXT_KEYED_SERVICE_H_