Fix counting of scanned bytes in incremental marking step for large object.

src/incremental-marking.h

Index: src/incremental-marking.h
diff --git a/src/incremental-marking.h b/src/incremental-marking.h
index 47d5a518bf841076c805b27c5acc22719ab3f2b8..d47c300ef3f97893e3f018c0aab3a20c76856da9 100644
--- a/src/incremental-marking.h
+++ b/src/incremental-marking.h
@@ -220,6 +220,10 @@ class IncrementalMarking {
 
   void UncommitMarkingDeque();
 
+  void NotifyIncompleteScanOfObject(int unscanned_bytes) {
+    unscanned_bytes_of_large_object_ = unscanned_bytes;
+  }
+
  private:
   int64_t SpaceLeftInOldSpace();
 
@@ -274,6 +278,8 @@ class IncrementalMarking {
 
   int no_marking_scope_depth_;
 
+  int unscanned_bytes_of_large_object_;
+
   DISALLOW_IMPLICIT_CONSTRUCTORS(IncrementalMarking);
 };