Always terminate the task queue

BUG=none
LOG=n
TBR=hpayer@chromium.org

Review URL: https://codereview.chromium.org/107503005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18382 ce2b1a6d-e550-0410-aec6-3dcde31c8c00