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.
