Create ast/ and parsing/ subdirectories and move appropriate files

src/ast-expression-visitor.h

-// Copyright 2015 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_EXPRESSION_VISITOR_H_
-#define V8_AST_EXPRESSION_VISITOR_H_
-
-#include "src/allocation.h"
-#include "src/ast.h"
-#include "src/effects.h"
-#include "src/scopes.h"
-#include "src/type-info.h"
-#include "src/types.h"
-#include "src/zone.h"
-
-namespace v8 {
-namespace internal {
-
-// A Visitor over a CompilationInfo's AST that invokes
-// VisitExpression on each expression node.
-
-class AstExpressionVisitor : public AstVisitor {
- public:
-  AstExpressionVisitor(Isolate* isolate, Expression* root);
-  AstExpressionVisitor(uintptr_t stack_limit, Expression* root);
-  void Run();
-
- protected:
-  virtual void VisitExpression(Expression* expression) = 0;
-  int depth() { return depth_; }
-
- private:
-  void VisitDeclarations(ZoneList<Declaration*>* d) override;
-  void VisitStatements(ZoneList<Statement*>* s) override;
-
-  DEFINE_AST_VISITOR_SUBCLASS_MEMBERS();
-
-#define DECLARE_VISIT(type) void Visit##type(type* node) override;
-  AST_NODE_LIST(DECLARE_VISIT)
-#undef DECLARE_VISIT
-
-  Expression* root_;
-  int depth_;
-
-  DISALLOW_COPY_AND_ASSIGN(AstExpressionVisitor);
-};
-}  // namespace internal
-}  // namespace v8
-
-#endif  // V8_AST_EXPRESSION_VISITOR_H_