[parser] Refactor some CHECK_OK calls

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/base/hashmap.h"
@@ skipping 741 matching lines @@
   // Reporting errors.
   void ReportMessageAt(Scanner::Location location,
                        MessageTemplate::Template message,
                        const char* arg = NULL,
                        ParseErrorType error_type = kSyntaxError);
   void ReportMessageAt(int start_pos, int end_pos,
                        MessageTemplate::Template message,
                        const char* arg = NULL,
                        ParseErrorType error_type = kSyntaxError);
 
+  // A dummy function, just useful as an argument to CHECK_OK_CUSTOM.
+  static void Void() {}
+
   // "null" return type creators.
   static PreParserIdentifier EmptyIdentifier() {
     return PreParserIdentifier::Default();
   }
   static PreParserIdentifier EmptyIdentifierString() {
     return PreParserIdentifier::Default();
   }
   static PreParserExpression EmptyExpression() {
     return PreParserExpression::Default();
   }
@@ skipping 489 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