This makes them show up in the stack trace. Otherwise the stack frames
are identified as type STUB, and skipped by the iterator.

R=ahaas@chromium.org, jfb@chromium.org, titzer@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1878573003

Cr-Commit-Position: refs/heads/master@{#35621}