Also deletes lots of code that attempts to detect when the heap is
corrupt but would likely just crash if the heap was corrupt.

Bug: v8:7786
Change-Id: I2e6bbea2e393b0f640a9d7180114560e7f6d3670
Reviewed-on: https://chromium-review.googlesource.com/1140061Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54487}