Revert of Preparse top-level functions in discardable zones (patchset #2 id:20001 of https://codereview.chromium.org/2374963002/ )

Reason for revert:
Needed to revert https://codereview.chromium.org/2368313002 which slows down asm.js code

Original issue's description:
> Preparse top-level functions in discardable zones
>
> BUG=
>
> Committed: https://crrev.com/ff8cfa9e5e8495165291ddf6e01dba3f8cb5a177
> Cr-Commit-Position: refs/heads/master@{#39809}

TBR=marja@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=

Review-Url: https://codereview.chromium.org/2375013002
Cr-Commit-Position: refs/heads/master@{#39815}