[es7] implement exponentiation operator proposal

src/parsing/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_PARSING_PREPARSER_H
 #define V8_PARSING_PREPARSER_H
 
 #include "src/ast/scopes.h"
 #include "src/bailout-reason.h"
 #include "src/hashmap.h"
@@ skipping 903 matching lines @@
 
   inline PreParserExpression SpreadCall(PreParserExpression function,
                                         PreParserExpressionList args, int pos);
 
   inline PreParserExpression SpreadCallNew(PreParserExpression function,
                                            PreParserExpressionList args,
                                            int pos);
 
   inline void RewriteDestructuringAssignments() {}
 
+  inline PreParserExpression RewriteAssignExponentiation(
+      PreParserExpression left, PreParserExpression right, int pos) {
+    return left;
+  }
+
   inline void QueueDestructuringAssignmentForRewriting(PreParserExpression) {}
 
   void SetFunctionNameFromPropertyName(PreParserExpression,
                                        PreParserIdentifier) {}
   void SetFunctionNameFromIdentifierRef(PreParserExpression,
                                         PreParserExpression) {}
 
   inline PreParserExpression RewriteNonPattern(
       PreParserExpression expr, const ExpressionClassifier* classifier,
       bool* ok);
@@ skipping 227 matching lines @@
     const PreParserFormalParameters& parameters, FunctionKind kind,
     FunctionLiteral::FunctionType function_type, bool* ok) {
   return pre_parser_->ParseEagerFunctionBody(function_name, pos, parameters,
                                              kind, function_type, ok);
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_PREPARSER_H