Add toHTMLMarqueeElement, and use it.

Source/core/rendering/RenderMarquee.cpp

 /*
  * Copyright (C) 2006, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
@@ skipping 64 matching lines @@
     UseCounter::count(&document(), UseCounter::HTMLMarqueeElement);
 }
 
 RenderMarquee::~RenderMarquee()
 {
 }
 
 int RenderMarquee::marqueeSpeed() const
 {
     int result = style()->marqueeSpeed();
-    if (Node* node = this->node()) {
-        ASSERT(node->hasTagName(marqueeTag));
-        HTMLMarqueeElement* marqueeElt = static_cast<HTMLMarqueeElement*>(node);
-        result = max(result, marqueeElt->minimumDelay());
-    }
+    if (Node* node = this->node())
+        result = std::max(result, toHTMLMarqueeElement(node)->minimumDelay());
     return result;
 }
 
 EMarqueeDirection RenderMarquee::direction() const
 {
     // FIXME: Support the CSS3 "auto" value for determining the direction of the marquee.
     // For now just map MAUTO to MBACKWARD
     EMarqueeDirection result = style()->marqueeDirection();
     TextDirection dir = style()->direction();
     if (result == MAUTO)
@@ skipping 231 matching lines @@
             m_reset = true;
     }
 
     if (isHorizontal())
         layer()->scrollToXOffset(newPos);
     else
         layer()->scrollToYOffset(newPos);
 }
 
 } // namespace WebCore