services/ui: Create a proper component for the client-lib.

services/ui/public/cpp/window_surface_client.h

 // Copyright 2015 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 SERVICES_UI_PUBLIC_CPP_WINDOW_SURFACE_CLIENT_H_
 #define SERVICES_UI_PUBLIC_CPP_WINDOW_SURFACE_CLIENT_H_
 
 #include "mojo/public/cpp/bindings/array.h"
+#include "services/ui/public/cpp/ui_export.h"
 
 namespace cc {
 struct ReturnedResource;
 }
 
 namespace ui {
 
 class WindowSurface;
 
-class WindowSurfaceClient {
+class UI_EXPORT WindowSurfaceClient {
  public:
   virtual void OnResourcesReturned(
       WindowSurface* surface,
       mojo::Array<cc::ReturnedResource> resources) = 0;
 
  protected:
   virtual ~WindowSurfaceClient() {}
 };
 
 }  // namespace ui
 
 #endif  // SERVICES_UI_PUBLIC_CPP_WINDOW_SURFACE_CLIENT_H_