The current implemention breaks sloppy mode code that uses function
declarations inside blocks at top-level. Work is ongoing on a patch
to fix this issue, but in the meantime it seems reasonable to move
the feature out of staging.

Manual revert of commit 6e07f5a7.

R=littledan@chromium.org
BUG=chromium:535836
LOG=y

Review URL: https://codereview.chromium.org/1375213005

Cr-Commit-Position: refs/heads/master@{#31029}