No need to store invalid media queries.

Source/core/css/CSSGrammar.y.in

 /*
  *  Copyright (C) 2002-2003 Lars Knoll (knoll@kde.org)
  *  Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  *  Copyright (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  *  Copyright (C) 2008 Eric Seidel <eric@webkit.org>
  *  Copyright (C) 2012 Intel Corporation. All rights reserved.
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU Lesser General Public
  *  License as published by the Free Software Foundation; either
@@ skipping 548 matching lines @@
     }
     | ':' maybe_space expr {
         $$ = $3;
     }
     ;
 
 media_query_exp:
     '(' maybe_space IDENT maybe_space maybe_media_value closing_parenthesis maybe_space {
         parser->tokenToLowerCase($3);
         $$ = parser->createFloatingMediaQueryExp($3, $5);
+        if (!$$)
+            YYERROR;
     }
     | '(' error error_recovery closing_parenthesis {
         YYERROR;
     }
     ;
 
 media_query_exp_list:
     media_query_exp {
         $$ = parser->createFloatingMediaQueryExpList();
         $$->append(parser->sinkFloatingMediaQueryExp($1));
@@ skipping 1377 matching lines @@
 
 rule_error_recovery:
     /* empty */
   | rule_error_recovery error
   | rule_error_recovery invalid_square_brackets_block
   | rule_error_recovery invalid_parentheses_block
     ;
 
 %%