Port sky_shell to Linux for testing

sky/shell/ui/engine.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 SKY_SHELL_UI_ENGINE_H_
 #define SKY_SHELL_UI_ENGINE_H_
 
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
@@ skipping 21 matching lines @@
 
 class Engine : public UIDelegate,
                public ViewportObserver,
                public blink::ServiceProvider,
                public mojo::NavigatorHost,
                public blink::WebFrameClient,
                public blink::WebViewClient,
                public blink::SkyViewClient {
  public:
   struct Config {
+    Config();
+    ~Config();
+
     ServiceProviderContext* service_provider_context;
 
     base::WeakPtr<GPUDelegate> gpu_delegate;
     scoped_refptr<base::SingleThreadTaskRunner> gpu_task_runner;
   };
 
   explicit Engine(const Config& config);
   ~Engine() override;
 
   base::WeakPtr<Engine> GetWeakPtr();
@@ skipping 55 matching lines @@
 
   base::WeakPtrFactory<Engine> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(Engine);
 };
 
 }  // namespace shell
 }  // namespace sky
 
 #endif  // SKY_SHELL_UI_ENGINE_H_