1) As found by the GC fuzzer: missing HandleScopes.

2) The RecordSlot barrier was missing for NativeContext::AddDirtyJSWeakFactory.

3) Need Context::Scope to surround the cleanup function (if it results in an
error, we try to get native_context() from Isolate).

BUG=v8:8179,v8:8286

Change-Id: I2d995a76770658848e3c9629333bedbc2ef43b82
Reviewed-on: https://chromium-review.googlesource.com/c/1273051Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56529}