Currently the size of compaction spaces is not taken into account in
the Heap::CanExpandOldGeneration predicate. This can push the heap size
over the hard limit in some cases.

This patch makes Heap::CanExpandOldGeneration stricter and also fixes
the SelectGarbageCollector to prefer Mark-Compact near the hard limit.

Bug: chromium:784077
Change-Id: I00c7295eba8794a342dd6277a45f995529054b64
Reviewed-on: https://chromium-review.googlesource.com/779265Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49519}