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

Source/platform/fonts/GlyphPageTreeNodeTest.cpp

Index: Source/platform/fonts/GlyphPageTreeNodeTest.cpp
diff --git a/Source/platform/fonts/GlyphPageTreeNodeTest.cpp b/Source/platform/fonts/GlyphPageTreeNodeTest.cpp
index 3631bd163400c4ca61b4b3429390bc8f09e697ae..27f9ec22e9bb172a8584887ead2ab6409d748a59 100644
--- a/Source/platform/fonts/GlyphPageTreeNodeTest.cpp
+++ b/Source/platform/fonts/GlyphPageTreeNodeTest.cpp
@@ -18,7 +18,7 @@ public:
     static PassRefPtr<TestCustomFontData> create() { return adoptRef(new TestCustomFontData()); }
 private:
     TestCustomFontData() { }
-    virtual bool isLoadingFallback() const override { return true; }
+    bool isLoadingFallback() const override { return true; }
 };
 
 class TestSimpleFontData : public SimpleFontData {