More precisely specify property creation during structured clone

Explicitly reference the CreateDataProperty() internal algorithm
from ECMAScript which in turn relies on [[DefineOwnProperty]].
This removes any ambiguity about whether to use that or [[Set]]
when producing clones.

Resolves https://www.w3.org/Bugs/Public/show_bug.cgi?id=28052

source

@@ -8474,8 +8474,9 @@ interface <dfn>DOMStringMap</dfn> {
      exception, then abort the overall <span>structured clone</span> algorithm, with that exception
      being passed through to the caller.</p></li>
 
-     <li><p>Add a new property to <var>output</var> having the name <var>name</var>, and having the
-     value <var>cloned value</var>.</p></li>
+     <li><p>Add a new property to <var>output</var> having the name <var>name</var>, and having
+     the value <var>cloned value</var>, using
+     CreateDataProperty(<var>output</var>, <var>name</var>, <var>cloned value</var>).</p></li>
 
     </ol>