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

Source/core/fetch/MemoryCache.h

Index: Source/core/fetch/MemoryCache.h
diff --git a/Source/core/fetch/MemoryCache.h b/Source/core/fetch/MemoryCache.h
index 830969bbb79bc145f0cc5f15a79eb8754bdea4ec..27b44519c31d7d31122f0585e4eb28d659bd13f1 100644
--- a/Source/core/fetch/MemoryCache.h
+++ b/Source/core/fetch/MemoryCache.h
@@ -223,8 +223,8 @@ public:
     MemoryCacheLiveResourcePriority priority(Resource*) const;
 
     // TaskObserver implementation
-    virtual void willProcessTask() override;
-    virtual void didProcessTask() override;
+    void willProcessTask() override;
+    void didProcessTask() override;
 
     void pruneAll();