Use incremental marking deque in idle notification.

src/heap/mark-compact.cc

Index: src/heap/mark-compact.cc
diff --git a/src/heap/mark-compact.cc b/src/heap/mark-compact.cc
index 09eba59d3331f8e04497e7c3786163f8220c791f..847bdac1263db4c9de13aa624e934bb5edcbcdba 100644
--- a/src/heap/mark-compact.cc
+++ b/src/heap/mark-compact.cc
@@ -1944,11 +1944,6 @@ void MarkCompactCollector::MarkAllocationSite(AllocationSite* site) {
 }
 
 
-bool MarkCompactCollector::IsMarkingDequeEmpty() {
-  return marking_deque_.IsEmpty();
-}
-
-
 void MarkCompactCollector::MarkRoots(RootMarkingVisitor* visitor) {
   // Mark the heap roots including global variables, stack variables,
   // etc., and all objects reachable from them.