Remove Element#attributes.

sky/engine/core/editing/MarkupAccumulator.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2009, 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 282 matching lines @@
         appendText(result, toText(node));
         break;
     case Node::DOCUMENT_NODE:
         break;
     case Node::DOCUMENT_FRAGMENT_NODE:
         // Not implemented.
         break;
     case Node::ELEMENT_NODE:
         appendElement(result, toElement(node), namespaces);
         break;
-    case Node::ATTRIBUTE_NODE:
-        ASSERT_NOT_REACHED();
-        break;
     }
 }
 
 void MarkupAccumulator::appendEndMarkup(StringBuilder& result, const Element& element)
 {
     result.appendLiteral("</");
     result.append(element.tagQName().localName());
     result.append('>');
 }
 
 }