Switch CSSStyleDeclaration's property setter to new-style ExceptionState.

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 3115 matching lines @@
     return getPropertyCSSValue(propertyID);
 }
 
 String CSSComputedStyleDeclaration::getPropertyValueInternal(CSSPropertyID propertyID)
 {
     return getPropertyValue(propertyID);
 }
 
 void CSSComputedStyleDeclaration::setPropertyInternal(CSSPropertyID id, const String&, bool, ExceptionState& exceptionState)
 {
-    exceptionState.throwDOMException(NoModificationAllowedError, "Failed to set the '" + getPropertyNameString(id) + "' property on a computed 'CSSStyleDeclaration': computed styles are read-only.");
+    exceptionState.throwDOMException(NoModificationAllowedError, "This object is computed, and therefore read-only.");
 }
 
 const HashMap<AtomicString, String>* CSSComputedStyleDeclaration::variableMap() const
 {
     ASSERT(RuntimeEnabledFeatures::cssVariablesEnabled());
     Node* styledNode = this->styledNode();
     if (!styledNode)
         return 0;
     RefPtr<RenderStyle> style = styledNode->computedStyle(styledNode->isPseudoElement() ? NOPSEUDO : m_pseudoElementSpecifier);
     if (!style)
@@ skipping 79 matching lines @@
     static const CSSPropertyID propertiesAfterSlashSeperator[3] = { CSSPropertyBackgroundSize, CSSPropertyBackgroundOrigin,
                                                                     CSSPropertyBackgroundClip };
 
     RefPtr<CSSValueList> list = CSSValueList::createSlashSeparated();
     list->append(valuesForShorthandProperty(StylePropertyShorthand(CSSPropertyBackground, propertiesBeforeSlashSeperator, WTF_ARRAY_LENGTH(propertiesBeforeSlashSeperator))));
     list->append(valuesForShorthandProperty(StylePropertyShorthand(CSSPropertyBackground, propertiesAfterSlashSeperator, WTF_ARRAY_LENGTH(propertiesAfterSlashSeperator))));
     return list.release();
 }
 
 } // namespace WebCore