Reland of Preparse inner functions (new try) (patchset #1 id:1 of https://codereview.chromium.org/2373443003/ )

Reason for revert:
Stability thief found, relanding speculative reverts.

Original issue's description:
> Revert of Preparse inner functions (new try) (patchset #21 id:420001 of https://codereview.chromium.org/2352593002/ )
>
> Reason for revert:
> We currently have some stability issues on Canary. Let's reland this after we verified that we "fixed" Canary again.
>
> Original issue's description:
> > Preparse inner functions (new try)
> >
> > This is an overly pessimistic approach where PreParser only keeps
> > track of unresolved variables, but doesn't declare anything. This
> > will result in context-allocating variables in the outer function
> > unnecessarily, if the variable names clash with variable names
> > used by the inner function (even if the variables are not the
> > same). However, we have been unable to prove that this approach
> > wouldn't be good enough for the practical purposes.
> >
> > Fixes after the previous try ( https://codereview.chromium.org/2322243002/ ):
> > Keep the context-allocation decision stable when compiling fully eagerly.
> >
> > Tests which exercise this functionality:
> > mjsunit/fixed-context-shapes-when-recompiling.js
> >
> > Design document (chromium):
> >
> > https://docs.google.com/a/chromium.org/document/d/1rRv5JJZ0JpOZAZN2CSUwZPFJiBAdRnTiSYhazseNHFg/edit?usp=sharing
> >
> > BUG=
> >
> > Committed: https://crrev.com/7c73cf32c60484cdf37c84f1d61b4640e87068d7
> > Cr-Commit-Position: refs/heads/master@{#39719}
>
> TBR=verwaest@chromium.org,adamk@chromium.org,marja@chromium.org
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=
>
> Committed: https://crrev.com/1e6296b2a7cfc307fd9e722e619f42965da4a267
> Cr-Commit-Position: refs/heads/master@{#39730}

TBR=verwaest@chromium.org,adamk@chromium.org,marja@chromium.org,hablich@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/2377513006
Cr-Commit-Position: refs/heads/master@{#39755}