Show correct location of unhandled promise rejection messages when DevTools closed.

BUG=427954
R=yurys, pfeldman

Review URL: https://codereview.chromium.org/693183002

git-svn-id: svn://svn.chromium.org/blink/trunk@185363 bbb929c8-8fbe-4397-9dbb-9b2b20218538