Use idle task to perform incremental marking steps.

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index 6666b2c8238189ccfe269a8616c660550a69fe6a..f1e93ae4485c3c52a3973ccd8a94e89a6798b422 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -867,6 +867,8 @@ class Heap {
       intptr_t step_size_in_bytes, double deadline_in_ms,
       IncrementalMarking::StepActions step_actions);
 
+  bool TryFinalizeIdleIncrementalMarking(double idle_time_in_ms);
+
   inline void increment_scan_on_scavenge_pages() {
     scan_on_scavenge_pages_++;
     if (FLAG_gc_verbose) {
@@ -2241,10 +2243,6 @@ class Heap {
 
   void ReduceNewSpaceSize();
 
-  bool TryFinalizeIdleIncrementalMarking(
-      double idle_time_in_ms, size_t size_of_objects,
-      size_t mark_compact_speed_in_bytes_per_ms);
-
   GCIdleTimeHandler::HeapState ComputeHeapState();
 
   bool PerformIdleTimeAction(GCIdleTimeAction action,