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

Source/core/loader/PingLoader.h

Index: Source/core/loader/PingLoader.h
diff --git a/Source/core/loader/PingLoader.h b/Source/core/loader/PingLoader.h
index aecd6af0ad346049e56de0cdbb790384408e42d0..fef62e47f90bb64bdba8152089122b230ca43cd4 100644
--- a/Source/core/loader/PingLoader.h
+++ b/Source/core/loader/PingLoader.h
@@ -62,7 +62,7 @@ class CORE_EXPORT PingLoader : public RefCountedWillBeRefCountedGarbageCollected
     WTF_MAKE_NONCOPYABLE(PingLoader);
     WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED(PingLoader);
 public:
-    virtual ~PingLoader();
+    ~PingLoader() override;
 
     enum ViolationReportType {
         ContentSecurityPolicyViolationReport,
@@ -83,10 +83,10 @@ protected:
     void dispose();
 
 private:
-    virtual void didReceiveResponse(WebURLLoader*, const WebURLResponse&) override;
-    virtual void didReceiveData(WebURLLoader*, const char*, int, int) override;
-    virtual void didFinishLoading(WebURLLoader*, double, int64_t) override;
-    virtual void didFail(WebURLLoader*, const WebURLError&) override;
+    void didReceiveResponse(WebURLLoader*, const WebURLResponse&) override;
+    void didReceiveData(WebURLLoader*, const char*, int, int) override;
+    void didFinishLoading(WebURLLoader*, double, int64_t) override;
+    void didFail(WebURLLoader*, const WebURLError&) override;
 
     void timeout(Timer<PingLoader>*);