Do not create unresolved variables when parsing arrow functions lazily

src/parser.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_PARSER_H_
 #define V8_PARSER_H_
 
 #include "src/allocation.h"
 #include "src/ast.h"
 #include "src/compiler.h"  // For CachedDataMode
@@ skipping 867 matching lines @@
                                    Expression* tag);
   uint32_t ComputeTemplateLiteralHash(const TemplateLiteral* lit);
 
   Scanner scanner_;
   PreParser* reusable_preparser_;
   Scope* original_scope_;  // for ES5 function declarations in sloppy eval
   Target* target_stack_;  // for break, continue statements
   ParseData* cached_parse_data_;
 
   CompilationInfo* info_;
+  bool parsing_lazy_arrow_parameters_;  // for lazily parsed arrow functions.
 
   // Pending errors.
   bool has_pending_error_;
   Scanner::Location pending_error_location_;
   const char* pending_error_message_;
   const AstRawString* pending_error_arg_;
   const char* pending_error_char_arg_;
   bool pending_error_is_reference_error_;
 
   // Other information which will be stored in Parser and moved to Isolate after
@@ skipping 92 matching lines @@
 }
 
 
 Expression* ParserTraits::CloseTemplateLiteral(TemplateLiteralState* state,
                                                int start, Expression* tag) {
   return parser_->CloseTemplateLiteral(state, start, tag);
 }
 } }  // namespace v8::internal
 
 #endif  // V8_PARSER_H_