[es6] Fix and clean up recognition of simple parameter lists

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"  // TODO(titzer): remove this include dependency
@@ skipping 1136 matching lines @@
   // If bookmark is set, the (pre-)parser may decide to abort skipping
   // in order to force the function to be eagerly parsed, after all.
   // In this case, it'll reset the scanner using the bookmark.
   void SkipLazyFunctionBody(int* materialized_literal_count,
                             int* expected_property_count, bool* ok,
                             Scanner::BookmarkScope* bookmark = nullptr);
 
   PreParser::PreParseResult ParseLazyFunctionBodyWithPreParser(
       SingletonLogger* logger, Scanner::BookmarkScope* bookmark = nullptr);
 
-  bool IsSimpleParameterList(const ParserFormalParameters& parameters);
   Block* BuildParameterInitializationBlock(
       const ParserFormalParameters& parameters, bool* ok);
 
   // Consumes the ending }.
   ZoneList<Statement*>* ParseEagerFunctionBody(
       const AstRawString* function_name, int pos,
       const ParserFormalParameters& parameters,
       Variable* fvar, Token::Value fvar_init_op, FunctionKind kind, bool* ok);
 
   void ThrowPendingError(Isolate* isolate, Handle<Script> script);
@@ skipping 163 matching lines @@
     // conservative approximation necessary to account for parameters
     // that are assigned via the arguments array.
     var->set_maybe_assigned();
   }
 }
 
 
 void ParserTraits::AddParameterInitializationBlock(
     const ParserFormalParameters& parameters,
     ZoneList<v8::internal::Statement*>* body, bool* ok) {
-  if (!parser_->IsSimpleParameterList(parameters)) {
+  if (!parameters.is_simple) {
     auto* init_block =
         parser_->BuildParameterInitializationBlock(parameters, ok);
     if (!*ok) return;
     if (init_block != nullptr) {
       body->Add(init_block, parser_->zone());
     }
   }
 }
 } }  // namespace v8::internal
 
 #endif  // V8_PARSER_H_