Provide processing scope that makes it impossible to maintain locally
cached wrappers that could get invalidated in Blink and yield in
crashers.

Bug: chromium:843903, v8:8238
Change-Id: I7ba1905f6c77a97bcc61ac42f921dcac4772471f
Reviewed-on: https://chromium-review.googlesource.com/c/1349276
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57795}