Use idle task to perform incremental marking steps.

src/heap/incremental-marking.h

Index: src/heap/incremental-marking.h
diff --git a/src/heap/incremental-marking.h b/src/heap/incremental-marking.h
index 2c63cfcad6ade74752f06a6f51bc3cb127e29031..87eaf049ec160113e57ff39469f150d1703b124c 100644
--- a/src/heap/incremental-marking.h
+++ b/src/heap/incremental-marking.h
@@ -6,6 +6,7 @@
 #define V8_HEAP_INCREMENTAL_MARKING_H_
 
 
+#include "src/cancelable-task.h"
 #include "src/execution.h"
 #include "src/heap/mark-compact.h"
 #include "src/objects.h"
@@ -204,6 +205,12 @@ class IncrementalMarking {
 
   GCCallbackFlags CallbackFlags() const { return gc_callback_flags_; }
 
+  void ScheduleIncrementalMarkingTask();
+  void NotifyIncrementalMarkingTaskRunning();
+  bool IsIncrementalMarkingTaskPending() {
+    return pending_incremental_marking_task_;
+  }
+
  private:
   int64_t SpaceLeftInOldSpace();
 
@@ -264,8 +271,21 @@ class IncrementalMarking {
 
   GCCallbackFlags gc_callback_flags_;
 
+  bool pending_incremental_marking_task_;
+
   DISALLOW_IMPLICIT_CONSTRUCTORS(IncrementalMarking);
 };
+
+
+class IncrementalMarkingTask : public CancelableIdleTask {
+ public:
+  explicit IncrementalMarkingTask(Isolate* isolate)
+      : CancelableIdleTask(isolate) {}
+  // CancelableIdleTask overrides.
+  void RunInternal(double deadline_in_seconds) override;
+  enum Progress { kDone, kMoreWork };
+  static Progress Step(Heap* heap, double deadline_in_ms);
+};
 }
 }  // namespace v8::internal