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

Source/core/loader/DocumentThreadableLoader.h

 /*
  * Copyright (C) 2009, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2013, Intel Corporation
  *
  * 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.
@@ skipping 40 matching lines @@
 class KURL;
 class ResourceRequest;
 class SecurityOrigin;
 class ThreadableLoaderClient;
 
 class CORE_EXPORT DocumentThreadableLoader final : public ThreadableLoader, private ResourceOwner<RawResource>  {
     WTF_MAKE_FAST_ALLOCATED(DocumentThreadableLoader);
     public:
         static void loadResourceSynchronously(Document&, const ResourceRequest&, ThreadableLoaderClient&, const ThreadableLoaderOptions&, const ResourceLoaderOptions&);
         static PassRefPtr<DocumentThreadableLoader> create(Document&, ThreadableLoaderClient*, const ResourceRequest&, const ThreadableLoaderOptions&, const ResourceLoaderOptions&);
-        virtual ~DocumentThreadableLoader();
+        ~DocumentThreadableLoader() override;
 
-        virtual void overrideTimeout(unsigned long timeout) override;
+        void overrideTimeout(unsigned long timeout) override;
 
-        virtual void cancel() override;
+        void cancel() override;
         void setDefersLoading(bool);
 
     private:
         enum BlockingBehavior {
             LoadSynchronously,
             LoadAsynchronously
         };
 
         DocumentThreadableLoader(Document&, ThreadableLoaderClient*, BlockingBehavior, const ResourceRequest&, const ThreadableLoaderOptions&, const ResourceLoaderOptions&);
 
@@ skipping 92 matching lines @@
         // cross-origin redirects.
         // This is used to limit the number of redirects.
         // But this value is not the max number of total redirects allowed,
         // because same-origin redirects are not counted here.
         int m_corsRedirectLimit;
     };
 
 } // namespace blink
 
 #endif // DocumentThreadableLoader_h