FunctionState doesn't need to know AstNodeFactory.

src/ast/ast.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_AST_AST_H_
 #define V8_AST_AST_H_
 
 #include "src/ast/ast-value-factory.h"
 #include "src/ast/modules.h"
 #include "src/ast/variables.h"
@@ skipping 3051 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(AstTraversalVisitor);
 };
 
 // ----------------------------------------------------------------------------
 // AstNode factory
 
 class AstNodeFactory final BASE_EMBEDDED {
  public:
   explicit AstNodeFactory(AstValueFactory* ast_value_factory)
-      : local_zone_(ast_value_factory->zone()),
-        parser_zone_(ast_value_factory->zone()),
-        ast_value_factory_(ast_value_factory) {}
+      : local_zone_(nullptr),
+        parser_zone_(nullptr),
+        ast_value_factory_(ast_value_factory) {
+    if (ast_value_factory != nullptr) {
+      local_zone_ = ast_value_factory->zone();
+      parser_zone_ = ast_value_factory->zone();
+    }
+  }
 
   AstValueFactory* ast_value_factory() const { return ast_value_factory_; }
+  void set_ast_value_factory(AstValueFactory* ast_value_factory) {
+    ast_value_factory_ = ast_value_factory;
+    local_zone_ = ast_value_factory->zone();
+    parser_zone_ = ast_value_factory->zone();
+  }
 
   VariableDeclaration* NewVariableDeclaration(VariableProxy* proxy,
                                               VariableMode mode, Scope* scope,
                                               int pos) {
     return new (parser_zone_)
         VariableDeclaration(parser_zone_, proxy, mode, scope, pos);
   }
 
   FunctionDeclaration* NewFunctionDeclaration(VariableProxy* proxy,
                                               VariableMode mode,
@@ skipping 456 matching lines @@
                                     : NULL;                                   \
   }
 AST_NODE_LIST(DECLARE_NODE_FUNCTIONS)
 #undef DECLARE_NODE_FUNCTIONS
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_AST_AST_H_