[heap] Handle edge case in NewSpaceAllocationCounter test

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 a6cc7e825150b0d2def3fc00b2aa815caa532caa..87e9838ea61fe2870c5b4cbdd1394877432d7823 100644
--- a/test/cctest/heap/test-heap.cc
+++ b/test/cctest/heap/test-heap.cc
@@ -6159,6 +6159,7 @@ TEST(NewSpaceAllocationCounter) {
   Heap* heap = isolate->heap();
   size_t counter1 = heap->NewSpaceAllocationCounter();
   CcTest::CollectGarbage(NEW_SPACE);
+  CcTest::CollectGarbage(NEW_SPACE);  // Ensure new space is empty.
   const size_t kSize = 1024;
   AllocateInSpace(isolate, kSize, NEW_SPACE);
   size_t counter2 = heap->NewSpaceAllocationCounter();