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

Source/core/loader/EmptyClients.cpp

Index: Source/core/loader/EmptyClients.cpp
diff --git a/Source/core/loader/EmptyClients.cpp b/Source/core/loader/EmptyClients.cpp
index 0a79e34ee061806f5227b390bbc1ce9507d10fef..990fd3c71144b98dff6c519020d7ea11c6d75837 100644
--- a/Source/core/loader/EmptyClients.cpp
+++ b/Source/core/loader/EmptyClients.cpp
@@ -62,10 +62,10 @@ void fillWithEmptyClients(Page::PageClients& pageClients)
 
 class EmptyPopupMenu : public PopupMenu {
 public:
-    virtual void show(const FloatQuad&, const IntSize&, int) override { }
-    virtual void hide() override { }
-    virtual void updateFromElement() override { }
-    virtual void disconnectClient() override { }
+    void show(const FloatQuad&, const IntSize&, int) override { }
+    void hide() override { }
+    void updateFromElement() override { }
+    void disconnectClient() override { }
 };
 
 PassRefPtrWillBeRawPtr<PopupMenu> EmptyChromeClient::openPopupMenu(LocalFrame&, PopupMenuClient*)