It is possible that the foreground task is unable to clear the
scheduled unfinished work, eventually leading to an OOM.

We use either code_range on 64 bit, or the capacity of the code space,
as a heuristic for how much memory to use for compilation.

Bug: v8:6492, chromium:732010
Change-Id: I1e4c0825351a42fa0b8369ccc41800ac3445563d
Reviewed-on: https://chromium-review.googlesource.com/535017
Commit-Queue: Brad Nelson <bradnelson@chromium.org>
Reviewed-by: Brad Nelson <bradnelson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46017}