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

Source/core/svg/SVGFontFaceSource.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 SVGFontFaceSource_h
 #define SVGFontFaceSource_h
 
 #if ENABLE(SVG_FONTS)
 
 #include "core/css/CSSFontFaceSource.h"
 
 namespace WebCore {
 
 class SVGFontFaceElement;
 
 class SVGFontFaceSource : public CSSFontFaceSource {
 public:
-    SVGFontFaceSource(PassRefPtr<SVGFontFaceElement>);
+    SVGFontFaceSource(SVGFontFaceElement*);
 
 private:
     virtual PassRefPtr<SimpleFontData> createFontData(const FontDescription&) OVERRIDE;
 
-    RefPtr<SVGFontFaceElement> m_svgFontFaceElement;
+    // This is a raw ptr as the element resides in the same document as the FontFace. This is to avoid a reference cycle.
+    // FIXME: Oilpan: This should be a Member when we move SVGFontFaceElement to oilpan.
+    SVGFontFaceElement* m_svgFontFaceElement;
 };
 
 } // namespace WebCore
 
 #endif // ENABLE(SVG_FONTS)
 #endif