[es6] re-implement rest parameters via desugaring

src/preparser.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_PREPARSER_H
 #define V8_PREPARSER_H
 
 #include "src/v8.h"
 
 #include "src/bailout-reason.h"
@@ skipping 3637 matching lines @@
       if (!*ok) return -1;
     } while (!parsing_state->has_rest && Check(Token::COMMA));
 
     if (parsing_state->has_rest && peek() == Token::COMMA) {
       ReportMessageAt(scanner()->peek_location(),
                       MessageTemplate::kParamAfterRest);
       *ok = false;
       return -1;
     }
   }
-
   return parameter_count;
 }
 
 
 template <class Traits>
 void ParserBase<Traits>::CheckArityRestrictions(
     int param_count, FunctionLiteral::ArityRestriction arity_restriction,
     bool has_rest, int formals_start_pos, int formals_end_pos, bool* ok) {
   switch (arity_restriction) {
     case FunctionLiteral::GETTER_ARITY:
@@ skipping 311 matching lines @@
       *ok = false;
       return;
     }
     has_seen_constructor_ = true;
     return;
   }
 }
 } }  // v8::internal
 
 #endif  // V8_PREPARSER_H