Fix a bug in the pause after download change that was recently committed, trying to terminate a paused worker would hang.

TBR=jochen
BUG=371671

Review URL: https://codereview.chromium.org/337223004

git-svn-id: svn://svn.chromium.org/blink/trunk@176948 bbb929c8-8fbe-4397-9dbb-9b2b20218538