Add unit test for GlyphPageTreeNode.

Source/platform/fonts/SimpleFontData.h

 /*
  * This file is part of the internal font implementation.
  *
  * Copyright (C) 2006, 2008, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2007-2008 Torch Mobile, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 156 matching lines @@
 
     bool canRenderCombiningCharacterSequence(const UChar*, size_t) const;
 
     bool applyTransforms(GlyphBufferGlyph*, GlyphBufferAdvance*, size_t, TypesettingFeatures) const
     {
         return false;
     }
 
     PassRefPtr<CustomFontData> customFontData() const { return m_customFontData; }
 
-private:
+    // Implemented by the platform.
+    virtual bool fillGlyphPage(GlyphPage* pageToFill, unsigned offset, unsigned length, UChar* buffer, unsigned bufferLength) const;
+
+protected:
     SimpleFontData(const FontPlatformData&, PassRefPtr<CustomFontData> customData, bool isTextOrientationFallback = false);
 
     SimpleFontData(PassRefPtr<CustomFontData> customData, float fontSize, bool syntheticBold, bool syntheticItalic);
 
+private:
     void platformInit();
     void platformGlyphInit();
     void platformCharWidthInit();
     void platformDestroy();
 
     void initCharWidths();
 
     PassRefPtr<SimpleFontData> createScaledFontData(const FontDescription&, float scaleFactor) const;
     PassRefPtr<SimpleFontData> platformCreateScaledFontData(const FontDescription&, float scaleFactor) const;
 
@@ skipping 98 matching lines @@
 #endif
     else
         width = platformWidthForGlyph(glyph);
 
     m_glyphToWidthMap.setMetricsForGlyph(glyph, width);
     return width;
 }
 
 } // namespace WebCore
 #endif // SimpleFontData_h