[heap] Reland use larger marking steps during external allocation pressure

This reverts commit 195eab46.

BUG=chromium:626082, chromium:728228

Review-Url: https://codereview.chromium.org/2931393002
Cr-Commit-Position: refs/heads/master@{#45843}

src/heap/heap.cc

@@ -952,15 +952,13 @@ void Heap::ReportExternalMemoryPressure() {
     }
   } else {
     // Incremental marking is turned on an has already been started.
-    const double pressure =
-        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() +
-                            pressure * kMaxStepSizeOnExternalLimit;
+    const double kMinStepSize = 5;
+    const double kMaxStepSize = 10;
+    const double ms_step =
+        Min(kMaxStepSize,
+            Max(kMinStepSize, static_cast<double>(external_memory_) /
+                                  external_memory_limit_ * kMinStepSize));
+    const double deadline = MonotonicallyIncreasingTimeInMs() + ms_step;
     incremental_marking()->AdvanceIncrementalMarking(
         deadline, IncrementalMarking::GC_VIA_STACK_GUARD,
         IncrementalMarking::FORCE_COMPLETION, StepOrigin::kV8);