Revert of [heap] Use larger marking steps during external allocation pressure (patchset #4 id:60001 of https://codereview.chromium.org/2927553003/ )

Reason for revert:
Blocks the roll. Fails some layout tests:
https://build.chromium.org/p/tryserver.v8/builders/v8_linux_blink_rel/builds/21757

STDERR: # Fatal error in ../../v8/src/heap/heap.cc, line 957
STDERR: # Check failed: 1.0 <= pressure (1 vs. -0.00503761).

Original issue's description:
> [heap] Use larger marking steps during external allocation pressure
>
> BUG=chromium:626082, chromium:728228
>
> Review-Url: https://codereview.chromium.org/2927553003
> Cr-Commit-Position: refs/heads/master@{#45784}
> Committed: https://chromium.googlesource.com/v8/v8/+/8d75644fc0ce1cee5d6eca42006f4c4aa89e9b86

TBR=ulan@chromium.org,hpayer@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:626082, chromium:728228

Review-Url: https://codereview.chromium.org/2925333002
Cr-Commit-Position: refs/heads/master@{#45797}