[builtins] FastNewFunctionContextStub becomes a builtin

src/code-factory.cc

Index: src/code-factory.cc
diff --git a/src/code-factory.cc b/src/code-factory.cc
index 7d48cb15e221e16cac4cae154da3de008e4c4f65..634f91e9b8c9975aa908b2ffe22abb4d903182b9 100644
--- a/src/code-factory.cc
+++ b/src/code-factory.cc
@@ -359,8 +359,8 @@ Callable CodeFactory::FastCloneShallowObject(Isolate* isolate, int length) {
 // static
 Callable CodeFactory::FastNewFunctionContext(Isolate* isolate,
                                              ScopeType scope_type) {
-  FastNewFunctionContextStub stub(isolate, scope_type);
-  return make_callable(stub);
+  return Callable(isolate->builtins()->NewFunctionContext(scope_type),
+                  FastNewFunctionContextDescriptor(isolate));
 }
 
 // static