Unreviewed, upload two missing test files in the commit r174677.

* mathml/presentation/mo-stretch-update-expected.html: Added.
* mathml/presentation/mo-stretch-update.html: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@176543 268f45cc-cd09-0410-ab3c-d52691b4dbfc