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

Source/core/fetch/DocumentResourceReference.h

Index: Source/core/fetch/DocumentResourceReference.h
diff --git a/Source/core/fetch/DocumentResourceReference.h b/Source/core/fetch/DocumentResourceReference.h
index d67cb55bed5e333e65b79adcff9eb1574752bf94..46f9bf5167a4579d30d88c50c3521426ec7df47a 100644
--- a/Source/core/fetch/DocumentResourceReference.h
+++ b/Source/core/fetch/DocumentResourceReference.h
@@ -34,7 +34,7 @@ namespace blink {
 class DocumentResourceReference final : public DocumentResourceClient {
 public:
     DocumentResourceReference(DocumentResource* document) : m_document(document) { m_document->addClient(this); }
-    virtual ~DocumentResourceReference() { m_document->removeClient(this); }
+    ~DocumentResourceReference() override { m_document->removeClient(this); }
     DocumentResource* document() { return m_document.get(); }
 private:
     ResourcePtr<DocumentResource> m_document;