Revert of [heap] Use larger marking steps during external allocation pressure...

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}

src/heap/heap.cc

@@ -953,12 +953,14 @@ void Heap::ReportExternalMemoryPressure() {
   } else {
     // Incremental marking is turned on an has already been started.
     const double pressure =
-        static_cast<double>(external_memory_) / external_memory_limit_;
-    DCHECK_LE(1.0, pressure);
-    const double kMinStepSize = 5;
-    const double kMaxStepSize = 10;
+        static_cast<double>(external_memory_ -
+                            external_memory_at_last_mark_compact_ -
+                            kExternalAllocationSoftLimit) /
+        external_memory_hard_limit();
+    DCHECK_GE(1, pressure);
+    const double kMaxStepSizeOnExternalLimit = 25;
     const double deadline = MonotonicallyIncreasingTimeInMs() +
-                            Min(pressure * kMinStepSize, kMaxStepSize);
+                            pressure * kMaxStepSizeOnExternalLimit;
     incremental_marking()->AdvanceIncrementalMarking(
         deadline, IncrementalMarking::GC_VIA_STACK_GUARD,
         IncrementalMarking::FORCE_COMPLETION, StepOrigin::kV8);