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

Source/platform/graphics/paint/DisplayItem.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef DisplayItem_h
 #define DisplayItem_h
 
 #include "platform/PlatformExport.h"
 #include "platform/graphics/ListContainer.h"
 #include "platform/graphics/paint/DisplayItemClient.h"
@@ skipping 336 matching lines @@
 #ifndef NDEBUG
     WTF::String m_clientDebugString;
 #endif
 };
 
 class PLATFORM_EXPORT PairedBeginDisplayItem : public DisplayItem {
 protected:
     PairedBeginDisplayItem(const DisplayItemClientWrapper& client, Type type) : DisplayItem(client, type) { }
 
 private:
-    virtual bool isBegin() const override final { return true; }
+    bool isBegin() const final { return true; }
 };
 
 class PLATFORM_EXPORT PairedEndDisplayItem : public DisplayItem {
 protected:
     PairedEndDisplayItem(const DisplayItemClientWrapper& client, Type type) : DisplayItem(client, type) { }
 
 #if ENABLE(ASSERT)
-    virtual bool isEndAndPairedWith(DisplayItem::Type otherType) const override = 0;
+    bool isEndAndPairedWith(DisplayItem::Type otherType) const override = 0;
 #endif
 
 private:
-    virtual bool isEnd() const override final { return true; }
+    bool isEnd() const final { return true; }
 };
 
 } // namespace blink
 
 #endif // DisplayItem_h