Revert of "[heap] Add more tasks for parallel compaction"

Revert of "[heap] Add more tasks for parallel compaction" (patchset #4 id:100001 of https://codereview.chromium.org/1365743003/ )

Reason for revert:
failing again: https://chromegw.corp.google.com/i/client.v8/builders/V8%20Mac/builds/4505/steps/Mozilla%20%28flakes%29/logs/regress-416628

Original issue's description:
> Reland of "[heap] Add more tasks for parallel compaction"
>
> - We now compute the number of parallel compaction tasks, depending on the
>   evacuation candidate list, the number of cores, and some hard limit.
> - Free memory is moved over to compaction tasks (up to some limit)
> - Moving over memory is done by dividing the free list of a given space up among
>   other free lists. Since this is potentially slow we limit the maximum amount
>   of moved memory.
>
> This reverts commit bfccd5187ceb21c99feea4538e08ca7aef48b65b.
>
> BUG=chromium:524425
> LOG=N
>
> Committed: https://crrev.com/7e283d746a194ceaaca114e2ba17504653d6a109
> Cr-Commit-Position: refs/heads/master@{#30945}

TBR=hpayer@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:524425
Committed: https://crrev.com/26f36f1092242bf350281db44bbcfe160ff1ca96
Cr-Commit-Position: refs/heads/master@{#30947}

[Michael Lippautz, 2015-09-25 15:40:10]

Created Revert of "[heap] Add more tasks for parallel compaction"

[commit-bot: I haz the power, 2015-09-25 15:40:19]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1371653002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1371653002/1

[commit-bot: I haz the power, 2015-09-25 15:40:33]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-25 15:41:29]

Patchset 1 (id:??) landed as
https://crrev.com/26f36f1092242bf350281db44bbcfe160ff1ca96
Cr-Commit-Position: refs/heads/master@{#30947}