Implement the function.sent 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 780 matching lines @@
                                                 int pos) {
     return PreParserExpression::SuperCallReference();
   }
 
   static PreParserExpression NewTargetExpression(Scope* scope,
                                                  PreParserFactory* factory,
                                                  int pos) {
     return PreParserExpression::Default();
   }
 
+  static PreParserExpression FunctionSentExpression(Scope* scope,
+                                                    PreParserFactory* factory,
+                                                    int pos) {
+    return PreParserExpression::Default();
+  }
+
   static PreParserExpression DefaultConstructor(bool call_super, Scope* scope,
                                                 int pos, int end_pos) {
     return PreParserExpression::Default();
   }
 
   static PreParserExpression ExpressionFromLiteral(
       Token::Value token, int pos, Scanner* scanner,
       PreParserFactory* factory) {
     return PreParserExpression::Default();
   }
@@ skipping 345 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