sky/shell should link with sky/engine

sky/engine/public/web/WebViewClient.h

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 44 matching lines @@
 class WebURLRequest;
 class WebView;
 class WebWidget;
 struct WebConsoleMessage;
 struct WebPoint;
 struct WebRect;
 struct WebSize;
 
 class WebViewClient {
 public:
-    virtual ServiceProvider& services() = 0;
+    virtual ServiceProvider* services() { return nullptr; }
 
     // Initialize compositing for this widget.
     virtual void initializeLayerTreeView() { BLINK_ASSERT_NOT_REACHED(); };
 
     // Called when the page should pump a frame.
     virtual void scheduleVisualUpdate() { }
 
     // TODO(esprehn): Sky needs to implement these to control the mojo::View.
 
     // Called to get/set the position of the widget in screen coordinates.
@@ skipping 79 matching lines @@
         return WebPageVisibilityStateVisible;
     }
 
 protected:
     ~WebViewClient() { }
 };
 
 } // namespace blink
 
 #endif  // SKY_ENGINE_PUBLIC_WEB_WEBVIEWCLIENT_H_