Introduce DEFINE_CONTENT_DATA_TYPE_CASTS, and use it

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 1328 matching lines @@
     list->append(zoomAdjustedPixelValueForLength(fillSize.size.width(), style));
     list->append(zoomAdjustedPixelValueForLength(fillSize.size.height(), style));
     return list.release();
 }
 
 static PassRefPtrWillBeRawPtr<CSSValue> valueForContentData(const RenderStyle& style)
 {
     RefPtrWillBeRawPtr<CSSValueList> list = CSSValueList::createSpaceSeparated();
     for (const ContentData* contentData = style.contentData(); contentData; contentData = contentData->next()) {
         if (contentData->isCounter()) {
-            const CounterContent* counter = static_cast<const CounterContentData*>(contentData)->counter();
+            const CounterContent* counter = toCounterContentData(contentData)->counter();
             ASSERT(counter);
             list->append(cssValuePool().createValue(counter->identifier(), CSSPrimitiveValue::CSS_COUNTER_NAME));
         } else if (contentData->isImage()) {
-            const StyleImage* image = static_cast<const ImageContentData*>(contentData)->image();
+            const StyleImage* image = toImageContentData(contentData)->image();
             ASSERT(image);
             list->append(image->cssValue());
-        } else if (contentData->isText())
-            list->append(cssValuePool().createValue(static_cast<const TextContentData*>(contentData)->text(), CSSPrimitiveValue::CSS_STRING));
+        } else if (contentData->isText()) {
+            list->append(cssValuePool().createValue(toTextContentData(contentData)->text(), CSSPrimitiveValue::CSS_STRING));
+        }
     }
     return list.release();
 }
 
 static PassRefPtrWillBeRawPtr<CSSValue> valueForCounterDirectives(const RenderStyle& style, CSSPropertyID propertyID)
 {
     const CounterDirectiveMap* map = style.counterDirectives();
     if (!map)
         return nullptr;
 
@@ skipping 1760 matching lines @@
     return list.release();
 }
 
 void CSSComputedStyleDeclaration::trace(Visitor* visitor)
 {
     visitor->trace(m_node);
     CSSStyleDeclaration::trace(visitor);
 }
 
 } // namespace blink