Do not stop profiling if all finished profiles were deleted

Deleting finished profiles shouldn't interrupt profile recording.

BUG=chromium:327298
LOG=N
R=alph@chromium.org, jkummerow@chromium.org

Review URL: https://codereview.chromium.org/103893003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18302 ce2b1a6d-e550-0410-aec6-3dcde31c8c00