When compaction is aborted we used to remember this in a data structure
and in a flag on the page that was set by the compacting thread.

Setting the flag races with other threads recording old-to-old slots and
thus checking the page's flags.

Since we already record the page in a data structure, we can delay
setting the flag on the page until post processing aborted compaction
pages right after the evacuation phase.

Bug: v8:7125
Change-Id: I20d109f0f69cf8eab90ed355c113abc6a2f606da
Reviewed-on: https://chromium-review.googlesource.com/789931Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49625}