Unable to round-trip tab character using XMLHttpRequest and XMLSerializer

Use case:

Assume JavaScript in a Mozilla Firefox extension.
1) Create or open a new XML document for modification using DOM.
2) Set an XML attribute value containing a tab character.  e.g., 
node.setAttribute("someName", "some /t Value");
3) Save the XML using XMLSerializer.
4) Re-read the XML using XMLHttpRequest.

The problem is that this currently would be read back in as "some Value" 
instead of "some /t Value".

Verified that the saved XML contains 13 characters, including 
[space,tab,space].

Missing the tab when reading this is somewhat expected, per what I 
understand of the W3C specification regarding attribute normalization: 
http://www.w3.org/TR/2000/REC-xml-20001006#sec-white-space

When manually changing the saved XML to instead use a character entity 
("some 	 Value"), the read from XMLHttpRequest works as desired, 
returning "some /t Value" for the "someName" attribute.

I am unable to determine how to save values with character entities 
using XMLSerializer.  It properly escapes values such as '&', replacing 
it with "&".  However, as such, trying to save "	" results in 
the entity being escaped "	".  This should be expected, but the 
question remains: How can a character entity be written using XMLSerializer?

(I just verified that using Apache Xalan-J (the default JAXP transformer 
under Java 6) serializes '/t' using a character entity.)

--
Mark A. Ziesemer
www.ziesemer.com