Optimize @@species based on a global 'protector' cell

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index bcb72f5866624edaacc31f3659f4b34e6cf6e87e..c4f64def688ffbe000f39df12345b15dd42b51a5 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -188,7 +188,8 @@ namespace internal {
   V(Object, weak_stack_trace_list, WeakStackTraceList)                         \
   V(Object, noscript_shared_function_infos, NoScriptSharedFunctionInfos)       \
   V(Map, bytecode_array_map, BytecodeArrayMap)                                 \
-  V(WeakCell, empty_weak_cell, EmptyWeakCell)
+  V(WeakCell, empty_weak_cell, EmptyWeakCell)                                  \
+  V(PropertyCell, species_protector, SpeciesProtector)
 
 // Entries in this list are limited to Smis and are not visited during GC.
 #define SMI_ROOT_LIST(V)                                                   \