Fix virtual/override/final usage in Source/platform/.

Source/platform/exported/WebURLResponse.cpp

Index: Source/platform/exported/WebURLResponse.cpp
diff --git a/Source/platform/exported/WebURLResponse.cpp b/Source/platform/exported/WebURLResponse.cpp
index faf4d557638e29e84a8df8a7f5fc4a05d6282d72..48432e920ad5a1f6e8a35d94aa156933bc7febf3 100644
--- a/Source/platform/exported/WebURLResponse.cpp
+++ b/Source/platform/exported/WebURLResponse.cpp
@@ -49,7 +49,7 @@ class ExtraDataContainer : public ResourceResponse::ExtraData {
 public:
     static PassRefPtr<ExtraDataContainer> create(WebURLResponse::ExtraData* extraData) { return adoptRef(new ExtraDataContainer(extraData)); }
 
-    virtual ~ExtraDataContainer() { }
+    ~ExtraDataContainer() override {}
 
     WebURLResponse::ExtraData* extraData() const { return m_extraData.get(); }