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

Source/platform/graphics/paint/SubtreeDisplayItem.h

 // Copyright 2015 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 SubtreeDisplayItem_h
 #define SubtreeDisplayItem_h
 
 #include "platform/geometry/FloatRect.h"
 #include "platform/graphics/paint/DisplayItem.h"
 #include "wtf/Assertions.h"
 
 namespace blink {
 
 class PLATFORM_EXPORT SubtreeCachedDisplayItem : public DisplayItem {
 public:
     SubtreeCachedDisplayItem(const DisplayItemClientWrapper& client, Type type)
         : DisplayItem(client, type)
     {
         ASSERT(isSubtreeCachedType(type));
     }
 
-    virtual void replay(GraphicsContext&) override final { ASSERT_NOT_REACHED(); }
-    virtual void appendToWebDisplayItemList(WebDisplayItemList*) const override final { ASSERT_NOT_REACHED(); }
+    void replay(GraphicsContext&) final { ASSERT_NOT_REACHED(); }
+    void appendToWebDisplayItemList(WebDisplayItemList*) const final { ASSERT_NOT_REACHED(); }
 };
 
 class PLATFORM_EXPORT BeginSubtreeDisplayItem : public PairedBeginDisplayItem {
 public:
     BeginSubtreeDisplayItem(const DisplayItemClientWrapper& client, Type type)
         : PairedBeginDisplayItem(client, type)
     {
         ASSERT(isBeginSubtreeType(type));
     }
 };
 
 class PLATFORM_EXPORT EndSubtreeDisplayItem : public PairedEndDisplayItem {
 public:
     EndSubtreeDisplayItem(const DisplayItemClientWrapper& client, Type type)
         : PairedEndDisplayItem(client, type)
     {
         ASSERT(isEndSubtreeType(type));
     }
 
 #if ENABLE(ASSERT)
-    virtual bool isEndAndPairedWith(DisplayItem::Type otherType) const override final { return DisplayItem::isBeginSubtreeType(otherType); }
+    bool isEndAndPairedWith(DisplayItem::Type otherType) const final { return DisplayItem::isBeginSubtreeType(otherType); }
 #endif
 };
 
 } // namespace blink
 
 #endif // SubtreeDisplayItem_h