Fix idle step marking after 9d7ebc.

src/heap/incremental-marking.cc

Index: src/heap/incremental-marking.cc
diff --git a/src/heap/incremental-marking.cc b/src/heap/incremental-marking.cc
index 106b72e3c9729feeaa1069d0e8e2723edbfb0405..a277f7292e90e28bffe7e627095ae12051c7dc76 100644
--- a/src/heap/incremental-marking.cc
+++ b/src/heap/incremental-marking.cc
@@ -16,9 +16,9 @@ namespace v8 {
 namespace internal {
 
 
-IncrementalMarking::StepActions IncrementalMarking::NoForcedStepActions() {
+IncrementalMarking::StepActions IncrementalMarking::IdleStepActions() {
   return StepActions(IncrementalMarking::NO_GC_VIA_STACK_GUARD,
-                     IncrementalMarking::DO_NOT_FORCE_MARKING,
+                     IncrementalMarking::FORCE_MARKING,
                      IncrementalMarking::DO_NOT_FORCE_COMPLETION);
 }