[heap] Limit friendship of the Heap class to essentials.

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index 5d67854462dbaa5d3a6967a5696014509f9e8cf1..91f4ecc7ae57ce75b9b2f5193c9b66a01508c15d 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -3303,6 +3303,11 @@ void Heap::CreateInitialObjects() {
   // Handling of script id generation is in Factory::NewScript.
   set_last_script_id(Smi::FromInt(v8::UnboundScript::kNoScriptId));
 
+  // Allocate the empty script.
+  Handle<Script> script = factory->NewScript(factory->empty_string());
+  script->set_type(Smi::FromInt(Script::TYPE_NATIVE));
+  set_empty_script(*script);
+
   Handle<PropertyCell> cell = factory->NewPropertyCell();
   cell->set_value(Smi::FromInt(Isolate::kArrayProtectorValid));
   set_array_protector(*cell);