As a first step towards moving accesses to the broker, this moves
heap accesses from BitsetType::Lub to the broker.

Bug: v8:7790
Change-Id: Ie240b84b979717caae42cb8aa06ee8d9877a446d
Reviewed-on: https://chromium-review.googlesource.com/1088695
Commit-Queue: Jaroslav Sevcik <jarin@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53571}