Turn MQ classes into thread safe

Source/core/css/MediaQuery.h

 /*
  * CSS Media Query
  *
  * Copyright (C) 2006 Kimmo Kinnunen <kimmo.t.kinnunen@nokia.com>.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
@@ skipping 29 matching lines @@
 
 typedef WillBeHeapVector<OwnPtrWillBeMember<MediaQueryExp> > ExpressionHeapVector;
 
 class MediaQuery : public NoBaseWillBeGarbageCollectedFinalized<MediaQuery> {
     WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
 public:
     enum Restrictor {
         Only, Not, None
     };
 
-    MediaQuery(Restrictor, const AtomicString& mediaType, PassOwnPtrWillBeRawPtr<ExpressionHeapVector> exprs);
+    MediaQuery(Restrictor, const String& mediaType, PassOwnPtrWillBeRawPtr<ExpressionHeapVector> exprs);
     ~MediaQuery();
 
     Restrictor restrictor() const { return m_restrictor; }
     const ExpressionHeapVector& expressions() const { return *m_expressions; }
-    const AtomicString& mediaType() const { return m_mediaType; }
+    const String& mediaType() const { return m_mediaType; }
     bool operator==(const MediaQuery& other) const;
     String cssText() const;
 
     PassOwnPtrWillBeRawPtr<MediaQuery> copy() const { return adoptPtrWillBeNoop(new MediaQuery(*this)); }
 
     void trace(Visitor*);
 
 private:
     MediaQuery(const MediaQuery&);
 
     Restrictor m_restrictor;
-    AtomicString m_mediaType;
+    String m_mediaType;
     OwnPtrWillBeMember<ExpressionHeapVector> m_expressions;
     String m_serializationCache;
 
     String serialize() const;
 };
 
 } // namespace
 
 #endif