Refactor duplicate logic in Ast{Traversal,Expression}Visitor

src/ast/ast.h

Index: src/ast/ast.h
diff --git a/src/ast/ast.h b/src/ast/ast.h
index bee0bab47e5640cbcf43c89e3739993d8fdfac73..ee04f00ab9ac80a4ad736cd83200b5066f1c4ea9 100644
--- a/src/ast/ast.h
+++ b/src/ast/ast.h
@@ -3053,20 +3053,26 @@ class AstVisitor BASE_EMBEDDED {
 class AstTraversalVisitor : public AstVisitor {
  public:
   explicit AstTraversalVisitor(Isolate* isolate);
+  explicit AstTraversalVisitor(uintptr_t stack_limit);
   virtual ~AstTraversalVisitor() {}
 
   // Iteration left-to-right.
   void VisitDeclarations(ZoneList<Declaration*>* declarations) override;
   void VisitStatements(ZoneList<Statement*>* statements) override;
-  void VisitExpressions(ZoneList<Expression*>* expressions) override;
 
 // Individual nodes
 #define DECLARE_VISIT(type) void Visit##type(type* node) override;
   AST_NODE_LIST(DECLARE_VISIT)
 #undef DECLARE_VISIT
 
+ protected:
+  int depth() { return depth_; }
+
  private:
   DEFINE_AST_VISITOR_SUBCLASS_MEMBERS();
+
+  int depth_;
+
   DISALLOW_COPY_AND_ASSIGN(AstTraversalVisitor);
 };