Implement experimental exponentiation operator

src/scanner.h

 // Copyright 2011 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.
 
 // Features shared by parsing and pre-parsing scanners.
 
 #ifndef V8_SCANNER_H_
 #define V8_SCANNER_H_
 
 #include "src/allocation.h"
@@ skipping 452 matching lines @@
   bool HarmonyClasses() const {
     return harmony_classes_;
   }
   void SetHarmonyClasses(bool classes) {
     harmony_classes_ = classes;
   }
   bool HarmonyTemplates() const { return harmony_templates_; }
   void SetHarmonyTemplates(bool templates) { harmony_templates_ = templates; }
   bool HarmonyUnicode() const { return harmony_unicode_; }
   void SetHarmonyUnicode(bool unicode) { harmony_unicode_ = unicode; }
+  bool HarmonyExponentiation() const { return harmony_exponentiation_; }
+  void SetHarmonyExponentiation(bool exp) { harmony_exponentiation_ = exp; }
 
   // Returns true if there was a line terminator before the peek'ed token,
   // possibly inside a multi-line comment.
   bool HasAnyLineTerminatorBeforeNext() const {
     return has_line_terminator_before_next_ ||
            has_multiline_comment_before_next_;
   }
 
   // Scans the input as a regular expression pattern, previous
   // character(s) must be /(=). Returns true if a pattern is scanned.
@@ skipping 254 matching lines @@
   // Whether we scan 'module', 'import', 'export' as keywords.
   bool harmony_modules_;
   // Whether we scan 0o777 and 0b111 as numbers.
   bool harmony_numeric_literals_;
   // Whether we scan 'class', 'extends', 'static' and 'super' as keywords.
   bool harmony_classes_;
   // Whether we scan TEMPLATE_SPAN and TEMPLATE_TAIL
   bool harmony_templates_;
   // Whether we allow \u{xxxxx}.
   bool harmony_unicode_;
+  // Whether we allow x ** y or x **= y
+  bool harmony_exponentiation_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_SCANNER_H_