Content property not found among indexed properties of computed style.

Source/core/css/CSSComputedStyleDeclaration.cpp

 /*
  * Copyright (C) 2004 Zack Rusin <zack@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007 Nicholas Shanks <webkit@nickshanks.com>
  * Copyright (C) 2011 Sencha, Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
@@ skipping 74 matching lines @@
     CSSPropertyBorderTopRightRadius,
     CSSPropertyBorderTopStyle,
     CSSPropertyBorderTopWidth,
     CSSPropertyBottom,
     CSSPropertyBoxShadow,
     CSSPropertyBoxSizing,
     CSSPropertyCaptionSide,
     CSSPropertyClear,
     CSSPropertyClip,
     CSSPropertyColor,
+    CSSPropertyContent,
     CSSPropertyCursor,
     CSSPropertyDirection,
     CSSPropertyDisplay,
     CSSPropertyEmptyCells,
     CSSPropertyFloat,
     CSSPropertyFontFamily,
     CSSPropertyFontKerning,
     CSSPropertyFontSize,
     CSSPropertyFontSizeAdjust,
     CSSPropertyFontStretch,
@@ skipping 584 matching lines @@
     exceptionState.throwDOMException(NoModificationAllowedError, "These styles are computed, and therefore the '" + getPropertyNameString(id) + "' property is read-only.");
 }
 
 DEFINE_TRACE(CSSComputedStyleDeclaration)
 {
     visitor->trace(m_node);
     CSSStyleDeclaration::trace(visitor);
 }
 
 } // namespace blink