Fix crasher when checking for "of", but next token has no literal buffer

src/preparser.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 644 matching lines @@
   ParseExpression(true, CHECK_OK);
   Expect(i::Token::RPAREN, CHECK_OK);
   ParseStatement(ok);
   return Statement::Default();
 }
 
 
 bool PreParser::CheckInOrOf() {
   if (peek() == i::Token::IN ||
       (allow_for_of() &&
+       peek() == i::Token::IDENTIFIER &&
        scanner_->is_next_contextual_keyword(v8::internal::CStrVector("of")))) {
     Next();
     return true;
   }
   return false;
 }
 
 
 PreParser::Statement PreParser::ParseForStatement(bool* ok) {
   // ForStatement ::
@@ skipping 1144 matching lines @@
       backing_store_.Add(static_cast<byte>((ascii_length >> 14) | 0x80u));
     }
     backing_store_.Add(static_cast<byte>((ascii_length >> 7) | 0x80u));
   }
   backing_store_.Add(static_cast<byte>(ascii_length & 0x7f));
 
   backing_store_.AddBlock(bytes);
   return backing_store_.EndSequence().start();
 }
 } }  // v8::preparser