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

Source/platform/graphics/BitmapPatternBase.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 BitmapPatternBase_h
 #define BitmapPatternBase_h
 
 #include "platform/graphics/Pattern.h"
 #include "third_party/skia/include/core/SkImageInfo.h"
 
 namespace blink {
 
 class PLATFORM_EXPORT BitmapPatternBase : public Pattern {
 public:
     BitmapPatternBase(RepeatMode, int64_t externalMemoryAllocated = 0);
-    virtual ~BitmapPatternBase();
+    ~BitmapPatternBase() override;
 
 protected:
-    virtual PassRefPtr<SkShader> createShader() override;
+    PassRefPtr<SkShader> createShader() override;
 
     virtual SkImageInfo getBitmapInfo() = 0;
     virtual void drawBitmapToCanvas(SkCanvas&, SkPaint&) = 0;
 };
 
 } // namespace
 
 #endif  /* BitmapPatternBase_h */