[heap] Ensure quick progress of incremental marking near OOM.

BUG=chromium:667388

Review-Url: https://codereview.chromium.org/2520963004
Cr-Commit-Position: refs/heads/master@{#41184}

src/heap/heap.h

@@ -1852,6 +1852,10 @@ class Heap {
     return (OldGenerationCapacity() + size) < MaxOldGenerationSize();
   }
 
+  bool IsCloseToOutOfMemory(size_t slack) {
+    return OldGenerationCapacity() + slack >= MaxOldGenerationSize();
+  }
+
   bool ShouldExpandOldGenerationOnAllocationFailure();
 
   enum class IncrementalMarkingLimit { kNoLimit, kSoftLimit, kHardLimit };

src/heap/incremental-marking.cc

@@ -1069,6 +1069,13 @@ size_t IncrementalMarking::StepSizeToMakeProgress() {
   // target step count are chosen based on benchmarks.
   const int kRampUpIntervalMs = 300;
   const size_t kTargetStepCount = 128;
+  const size_t kTargetStepCountAtOOM = 16;
+  size_t oom_slack = heap()->new_space()->Capacity() + 64 * MB;
+
+  if (heap()->IsCloseToOutOfMemory(oom_slack)) {
+    return heap()->PromotedSpaceSizeOfObjects() / kTargetStepCountAtOOM;
+  }
+
   size_t step_size = Max(initial_old_generation_size_ / kTargetStepCount,
                          IncrementalMarking::kAllocatedThreshold);
   double time_passed_ms =