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

Source/core/xmlhttprequest/XMLHttpRequestProgressEventThrottle.h

Index: Source/core/xmlhttprequest/XMLHttpRequestProgressEventThrottle.h
diff --git a/Source/core/xmlhttprequest/XMLHttpRequestProgressEventThrottle.h b/Source/core/xmlhttprequest/XMLHttpRequestProgressEventThrottle.h
index 7124bc7414c40b30c5b013b58941275990acca04..fde13a8b67309b596b6df61067c94bf395710d4b 100644
--- a/Source/core/xmlhttprequest/XMLHttpRequestProgressEventThrottle.h
+++ b/Source/core/xmlhttprequest/XMLHttpRequestProgressEventThrottle.h
@@ -55,7 +55,7 @@ public:
     {
         return adoptPtrWillBeNoop(new XMLHttpRequestProgressEventThrottle(eventTarget));
     }
-    virtual ~XMLHttpRequestProgressEventThrottle();
+    ~XMLHttpRequestProgressEventThrottle() override;
 
     enum DeferredEventAction {
         Ignore,
@@ -92,7 +92,7 @@ private:
     class DeferredEvent;
     static const double minimumProgressEventDispatchingIntervalInSeconds;
 
-    virtual void fired() override;
+    void fired() override;
     void dispatchDeferredEvent();
 
     // Non-Oilpan, keep a weak pointer to our XMLHttpRequest object as it is