This attaches a constructor to the bound function map so we can identify the creation context using the map, it chooses the bound-function map from the same realm as the target's creation context (additionally to avoid memory leaks and unnecessary transitions), and finally drops the loop unwrapping bound functions in GetCreationContext.

Bug: 
Change-Id: Icb6f4c29287f9cba69f11afbd070f52c0ad1aa16
Reviewed-on: https://chromium-review.googlesource.com/738097Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48956}