Remove Element#attributes.

sky/engine/core/editing/MarkupAccumulator.cpp

Index: sky/engine/core/editing/MarkupAccumulator.cpp
diff --git a/sky/engine/core/editing/MarkupAccumulator.cpp b/sky/engine/core/editing/MarkupAccumulator.cpp
index ea0262ebe1637f4daeca7f2438381819ef18ad49..66be4f54ae2310ab6cdefc31b80d05eb253f8e0b 100644
--- a/sky/engine/core/editing/MarkupAccumulator.cpp
+++ b/sky/engine/core/editing/MarkupAccumulator.cpp
@@ -300,9 +300,6 @@ void MarkupAccumulator::appendStartMarkup(StringBuilder& result, Node& node, Nam
     case Node::ELEMENT_NODE:
         appendElement(result, toElement(node), namespaces);
         break;
-    case Node::ATTRIBUTE_NODE:
-        ASSERT_NOT_REACHED();
-        break;
     }
 }