[es6] Fix scoping for default parameters in arrow functions

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, FunctionLiteral* root);
+  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) virtual void Visit##type(type* node) override;
   AST_NODE_LIST(DECLARE_VISIT)
 #undef DECLARE_VISIT
 
-  FunctionLiteral* root_;
+  Expression* root_;
   int depth_;
 
   DISALLOW_COPY_AND_ASSIGN(AstExpressionVisitor);
 };
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_AST_EXPRESSION_VISITOR_H_