Count closures using the feedback vector cell map, specialize if count==1.

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index 4451b5a6a5bc824c4fd2b5378ab99a3fce62c46c..3ca987faa7470132fbaf3c4e3524feeb29712c76 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -2333,6 +2333,9 @@ bool Heap::CreateInitialMaps() {
     ALLOCATE_MAP(CELL_TYPE, Cell::kSize, cell)
     ALLOCATE_MAP(PROPERTY_CELL_TYPE, PropertyCell::kSize, global_property_cell)
     ALLOCATE_MAP(WEAK_CELL_TYPE, WeakCell::kSize, weak_cell)
+    ALLOCATE_MAP(CELL_TYPE, Cell::kSize, no_closures_cell)
+    ALLOCATE_MAP(CELL_TYPE, Cell::kSize, one_closure_cell)
+    ALLOCATE_MAP(CELL_TYPE, Cell::kSize, many_closures_cell)
     ALLOCATE_MAP(FILLER_TYPE, kPointerSize, one_pointer_filler)
     ALLOCATE_MAP(FILLER_TYPE, 2 * kPointerSize, two_pointer_filler)