This ensures that the stack traces show up correctly in
DevTools. I will later extend it for source view.

R=kozyatinskiy@chromium.org, yangguo@chromium.org, titzer@chromium.org
BUG=chromium:613110

Review-Url: https://codereview.chromium.org/2420093002
Cr-Commit-Position: refs/heads/master@{#40392}