In release mode, statements like:

    var i;
    for (i of [0]) { let j; debugger; }

would end up with one more block scope than in the debug modes.

R=adamk@chromium.org, marja@chromium.org
BUG=
LOG=N

Review-Url: https://codereview.chromium.org/2347633002
Cr-Commit-Position: refs/heads/master@{#39465}