Move map retaining to finalization of incremental marking.

test/cctest/heap/test-heap.cc

Index: test/cctest/heap/test-heap.cc
diff --git a/test/cctest/heap/test-heap.cc b/test/cctest/heap/test-heap.cc
index cfb44ce104af47c3ccf5764b792538ca9e1ff8af..c4bf0f2f475c9928d67ce7dbce7b56be05bd90b5 100644
--- a/test/cctest/heap/test-heap.cc
+++ b/test/cctest/heap/test-heap.cc
@@ -5923,9 +5923,11 @@ void CheckMapRetainingFor(int n) {
   Handle<WeakCell> weak_cell = AddRetainedMap(isolate, heap);
   CHECK(!weak_cell->cleared());
   for (int i = 0; i < n; i++) {
+    SimulateIncrementalMarking(heap);
     heap->CollectGarbage(OLD_SPACE);
   }
   CHECK(!weak_cell->cleared());
+  SimulateIncrementalMarking(heap);
   heap->CollectGarbage(OLD_SPACE);
   CHECK(weak_cell->cleared());
 }