Ensure that each profiling entry ends with a new line.

Currently this does not happen if the message builder buffer is full.

R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/390803002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22368 ce2b1a6d-e550-0410-aec6-3dcde31c8c00