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

Source/platform/graphics/filters/SourceGraphic.h

Index: Source/platform/graphics/filters/SourceGraphic.h
diff --git a/Source/platform/graphics/filters/SourceGraphic.h b/Source/platform/graphics/filters/SourceGraphic.h
index 60a9d579f9eb47403943283b98a97646c62a9a8e..4eb56d74a2b559cbe7d54599cc2763bb40e423b7 100644
--- a/Source/platform/graphics/filters/SourceGraphic.h
+++ b/Source/platform/graphics/filters/SourceGraphic.h
@@ -31,15 +31,15 @@ namespace blink {
 class PLATFORM_EXPORT SourceGraphic : public FilterEffect {
 public:
     static PassRefPtrWillBeRawPtr<SourceGraphic> create(Filter*);
-    virtual ~SourceGraphic();
+    ~SourceGraphic() override;
 
     static const AtomicString& effectName();
 
-    virtual FloatRect determineAbsolutePaintRect(const FloatRect& requestedRect) override;
+    FloatRect determineAbsolutePaintRect(const FloatRect& requestedRect) override;
 
-    virtual FilterEffectType filterEffectType() const override { return FilterEffectTypeSourceInput; }
+    FilterEffectType filterEffectType() const override { return FilterEffectTypeSourceInput; }
 
-    virtual TextStream& externalRepresentation(TextStream&, int indention) const override;
+    TextStream& externalRepresentation(TextStream&, int indention) const override;
     PassRefPtr<SkImageFilter> createImageFilter(SkiaImageFilterBuilder*) override;
 
     void setPicture(PassRefPtr<const SkPicture>);