Scanner: remove PushBack calls when we're going to return ILLEGAL.

src/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_PREPARSER_H
 #define V8_PREPARSER_H
 
 #include "src/v8.h"
 
 #include "src/bailout-reason.h"
@@ skipping 1686 matching lines @@
     ReportMessage("unterminated_regexp");
     *ok = false;
     return Traits::EmptyExpression();
   }
 
   int literal_index = function_state_->NextMaterializedLiteralIndex();
 
   IdentifierT js_pattern = this->GetNextSymbol(scanner());
   if (!scanner()->ScanRegExpFlags()) {
     Next();
-    ReportMessage("invalid_regexp_flags");
+    ReportMessage("malformed_regexp_flags");
     *ok = false;
     return Traits::EmptyExpression();
   }
   IdentifierT js_flags = this->GetNextSymbol(scanner());
   Next();
   return factory()->NewRegExpLiteral(js_pattern, js_flags, literal_index, pos);
 }
 
 
 #define CHECK_OK  ok); \
@@ skipping 1123 matching lines @@
       DCHECK(IsAccessorAccessorConflict(old_type, type));
       // Both accessors of the same type.
       parser()->ReportMessage("accessor_get_set");
     }
     *ok = false;
   }
 }
 } }  // v8::internal
 
 #endif  // V8_PREPARSER_H