Fix virtual/override/final usage in Source/core/{fetch,loader,streams,xmlhttprequest}/.

Source/core/loader/FrameLoaderClient.h

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2012 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:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 55 matching lines @@
     class WebApplicationCacheHost;
     class WebApplicationCacheHostClient;
     class WebCookieJar;
     class WebRTCPeerConnectionHandler;
     class WebServiceWorkerProvider;
     class WebSocketHandle;
     class Widget;
 
     class CORE_EXPORT FrameLoaderClient : public FrameClient {
     public:
-        virtual ~FrameLoaderClient() { }
+        ~FrameLoaderClient() override {}
 
         virtual bool hasWebView() const = 0; // mainly for assertions
 
         virtual void dispatchWillSendRequest(DocumentLoader*, unsigned long identifier, ResourceRequest&, const ResourceResponse& redirectResponse) = 0;
         virtual void dispatchDidReceiveResponse(DocumentLoader*, unsigned long identifier, const ResourceResponse&) = 0;
         virtual void dispatchDidFinishLoading(DocumentLoader*, unsigned long identifier) = 0;
         virtual void dispatchDidLoadResourceFromMemoryCache(const ResourceRequest&, const ResourceResponse&) = 0;
 
         virtual void dispatchDidHandleOnloadEvents() = 0;
         virtual void dispatchDidReceiveServerRedirectForProvisionalLoad() = 0;
@@ skipping 151 matching lines @@
             BeforeUnloadHandler,
             UnloadHandler,
         };
         virtual void suddenTerminationDisablerChanged(bool present, SuddenTerminationDisablerType) { }
 
     };
 
 } // namespace blink
 
 #endif // FrameLoaderClient_h