Reason for revert:
OOMs in nosnap debug:
https://build.chromium.org/p/client.v8/builders/V8%20Linux%20-%20nosnap%20-%20debug/builds/9572
Original issue's description:
> [heap] New heuristics for starting of incremental marking.
>
> The motivation for this patch is to move more marking work to tasks.
> This is done by postponing the start of incremental marking until
> a marking task is running.
>
> This patch introduces a soft and a hard limits for incremental marking.
> When the soft limit is reached, the marking task is scheduled.
> If the hard limit is reached before the task is running, then
> incremental marking is started without waiting for the task.
>
> BUG=chromium:616434
> LOG=NO
>
> Committed: https://crrev.com/55683ddd2a32e0dfb8df66271fbf53e3618cce9d
> Cr-Commit-Position: refs/heads/master@{#39831}
TBR=hpayer@chromium.org,ulan@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:616434
Review-Url: https://codereview.chromium.org/2375983002
Cr-Commit-Position: refs/heads/master@{#39833}
a5440d1190