Added a runtime flag for the MQ parser

Source/core/css/MediaList.cpp

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2006, 2010, 2012 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 53 matching lines @@
         m_queries[i] = o.m_queries[i]->copy();
 }
 
 DEFINE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(MediaQuerySet)
 
 PassRefPtrWillBeRawPtr<MediaQuerySet> MediaQuerySet::create(const String& mediaString)
 {
     if (mediaString.isEmpty())
         return MediaQuerySet::create();
 
+    if (RuntimeEnabledFeatures::mediaQueryParserEnabled())
+        return MediaQueryParser::parse(mediaString);
+
     BisonCSSParser parser(strictCSSParserContext());
     return parser.parseMediaQueryList(mediaString);
 }
 
 PassRefPtrWillBeRawPtr<MediaQuerySet> MediaQuerySet::createOffMainThread(const String& mediaString)
 {
     if (mediaString.isEmpty())
         return MediaQuerySet::create();
 
     return MediaQueryParser::parse(mediaString);
@@ skipping 229 matching lines @@
                 }
             }
         }
     }
 
     if (suspiciousValue && !dotsPerPixelUsed)
         addResolutionWarningMessageToConsole(document, mediaQuerySet->mediaText(), suspiciousValue);
 }
 
 }