remove use of WriteAscii for vtune

R=svenpanne@chromium.org
BUG=

Review URL: https://codereview.chromium.org/14900003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14562 ce2b1a6d-e550-0410-aec6-3dcde31c8c00