[SVG Fonts] Fix <font-face> element leak document

Source/core/svg/SVGFontData.h

 /*
  * Copyright (C) 2008 Nikolas Zimmermann <zimmermann@kde.org>
  *
  * 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.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  */
 
 #ifndef SVGFontData_h
 #define SVGFontData_h
 
 #if ENABLE(SVG_FONTS)
 #include "platform/fonts/CustomFontData.h"
+#include "wtf/WeakPtr.h"
 #include "wtf/text/WTFString.h"
 
 namespace WebCore {
 
 class SimpleFontData;
 class SVGFontElement;
 class SVGFontFaceElement;
 
 class SVGFontData FINAL : public CustomFontData {
 public:
     static PassRefPtr<SVGFontData> create(SVGFontFaceElement* element)
     {
         return adoptRef(new SVGFontData(element));
     }
 
-    virtual ~SVGFontData() { }
+    virtual ~SVGFontData();
 
     virtual bool isSVGFont() const OVERRIDE { return true; };
+    virtual bool shouldSkipDrawing() const OVERRIDE;
     virtual void initializeFontData(SimpleFontData*, float fontSize) OVERRIDE;
     virtual float widthForSVGGlyph(Glyph, float fontSize) const OVERRIDE;
     virtual bool fillSVGGlyphPage(GlyphPage*, unsigned offset, unsigned length, UChar* buffer, unsigned bufferLength, const SimpleFontData*) const OVERRIDE;
     virtual bool applySVGGlyphSelection(WidthIterator&, GlyphData&, bool mirror, int currentCharacter, unsigned& advanceLength) const OVERRIDE;
 
-
-    SVGFontFaceElement* svgFontFaceElement() const { return m_svgFontFaceElement; }
+    SVGFontFaceElement* svgFontFaceElement() const;
 
     float horizontalOriginX() const { return m_horizontalOriginX; }
     float horizontalOriginY() const { return m_horizontalOriginY; }
     float horizontalAdvanceX() const { return m_horizontalAdvanceX; }
 
     float verticalOriginX() const { return m_verticalOriginX; }
     float verticalOriginY() const { return m_verticalOriginY; }
     float verticalAdvanceY() const { return m_verticalAdvanceY; }
 
 private:
     SVGFontData(SVGFontFaceElement*);
 
     bool fillBMPGlyphs(SVGFontElement*, GlyphPage* , unsigned offset, unsigned length, UChar* buffer, const SimpleFontData*) const;
     bool fillNonBMPGlyphs(SVGFontElement*, GlyphPage* , unsigned offset, unsigned length, UChar* buffer, const SimpleFontData*) const;
 
     String createStringWithMirroredCharacters(const String&) const;
 
     // Ths SVGFontFaceElement is kept alive --
     // 1) in the external font case: by the CSSFontFaceSource, which holds a reference to the external SVG document
     //    containing the element;
     // 2) in the in-document font case: by virtue of being in the document tree and making sure that when it is removed
     //    from the document, it removes the @font-face rule it owns from the document's mapped element sheet and forces
     //    a style update.
-    SVGFontFaceElement* m_svgFontFaceElement;
+    WeakPtr<SVGFontFaceElement> m_svgFontFaceElement;
 
     float m_horizontalOriginX;
     float m_horizontalOriginY;
     float m_horizontalAdvanceX;
 
     float m_verticalOriginX;
     float m_verticalOriginY;
     float m_verticalAdvanceY;
 };
 
 } // namespace WebCore
 
 #endif
 #endif // SVGFontData_h