This reverts commit 06f556d8.

Reason for revert: gc stress failures

Original change's description:
> [in-place weak refs] Replace Heap::script_list with a WeakArrayList.
> 
> BUG=v8:7308
> 
> Change-Id: Idd527fc2a2f5bde635441a511e424a83558ab969
> Reviewed-on: https://chromium-review.googlesource.com/1143467
> Commit-Queue: Marja Hölttä <marja@chromium.org>
> Reviewed-by: Jakob Gruber <jgruber@chromium.org>
> Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#54635}

TBR=ulan@chromium.org,marja@chromium.org,jgruber@chromium.org

Change-Id: I6908fa42fcf4a8916a1dc49b865526094f950c66
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:7308
Reviewed-on: https://chromium-review.googlesource.com/1148280Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54636}