the patch come from:
http://src.chromium.org/viewvc/chrome/trunk/src/third_party/libxml/src \
/include/libxml/tree.h?r1=56276&r2=149930
libxml2 2.9.0-rc1 and earlier, as used in Google Chrome before 21.0.1180.89,
does not properly support a cast of an unspecified variable during handling
of XSL transforms, which allows remote attackers to cause a denial of service
or possibly have unknown other impact via a crafted document, related to the
_xmlNs data structure in include/libxml/tree.h.
