No need to store invalid media queries.

Source/core/css/MediaQuery.cpp

 /*
  * CSS Media Query
  *
  * Copyright (C) 2005, 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 23 matching lines @@
 #include "wtf/MemoryInstrumentationVector.h"
 #include "wtf/NonCopyingSort.h"
 #include "wtf/text/StringBuilder.h"
 
 namespace WebCore {
 
 // http://dev.w3.org/csswg/cssom/#serialize-a-media-query
 String MediaQuery::serialize() const
 {
     StringBuilder result;
-    if (!m_ignored) {
-        switch (m_restrictor) {
-        case MediaQuery::Only:
-            result.append("only ");
-            break;
-        case MediaQuery::Not:
-            result.append("not ");
-            break;
-        case MediaQuery::None:
-            break;
-        }
+    switch (m_restrictor) {
+    case MediaQuery::Only:
+        result.append("only ");
+        break;
+    case MediaQuery::Not:
+        result.append("not ");
+        break;
+    case MediaQuery::None:
+        break;
+    }
 
-        if (m_expressions->isEmpty()) {
-            result.append(m_mediaType);
-            return result.toString();
-        }
+    if (m_expressions->isEmpty()) {
+        result.append(m_mediaType);
+        return result.toString();
+    }
 
-        if (m_mediaType != "all" || m_restrictor != None) {
-            result.append(m_mediaType);
-            result.append(" and ");
-        }
+    if (m_mediaType != "all" || m_restrictor != None) {
+        result.append(m_mediaType);
+        result.append(" and ");
+    }
 
-        result.append(m_expressions->at(0)->serialize());
-        for (size_t i = 1; i < m_expressions->size(); ++i) {
-            result.append(" and ");
-            result.append(m_expressions->at(i)->serialize());
-        }
-    } else {
-        // If query is invalid, serialized text should turn into "not all".
-        result.append("not all");
+    result.append(m_expressions->at(0)->serialize());
+    for (size_t i = 1; i < m_expressions->size(); ++i) {
+        result.append(" and ");
+        result.append(m_expressions->at(i)->serialize());
     }
     return result.toString();
 }
 
 static bool expressionCompare(const OwnPtr<MediaQueryExp>& a, const OwnPtr<MediaQueryExp>& b)
 {
     return codePointCompare(a->serialize(), b->serialize()) < 0;
 }
 
 MediaQuery::MediaQuery(Restrictor r, const String& mediaType, PassOwnPtr<Vector<OwnPtr<MediaQueryExp> > > exprs)
     : m_restrictor(r)
     , m_mediaType(mediaType.lower())
     , m_expressions(exprs)
-    , m_ignored(false)
 {
     if (!m_expressions) {
         m_expressions = adoptPtr(new Vector<OwnPtr<MediaQueryExp> >);
         return;
     }
 
     nonCopyingSort(m_expressions->begin(), m_expressions->end(), expressionCompare);
 
     // Remove all duplicated expressions.
     MediaQueryExp* key = 0;
     for (int i = m_expressions->size() - 1; i >= 0; --i) {
         MediaQueryExp* exp = m_expressions->at(i).get();
 
-        // If not all of the expressions are valid the media query must be ignored.
-        if (!m_ignored)
-            m_ignored = !exp->isValid();
-
         if (key && *exp == *key)
             m_expressions->remove(i);
         else
             key = exp;
     }
 }
 
 MediaQuery::MediaQuery(const MediaQuery& o)
     : m_restrictor(o.m_restrictor)
     , m_mediaType(o.m_mediaType)
     , m_expressions(adoptPtr(new Vector<OwnPtr<MediaQueryExp> >(o.m_expressions->size())))
-    , m_ignored(o.m_ignored)
     , m_serializationCache(o.m_serializationCache)
 {
     for (unsigned i = 0; i < m_expressions->size(); ++i)
         (*m_expressions)[i] = o.m_expressions->at(i)->copy();
 }
 
 MediaQuery::~MediaQuery()
 {
 }
 
@@ skipping 14 matching lines @@
 
 void MediaQuery::reportMemoryUsage(MemoryObjectInfo* memoryObjectInfo) const
 {
     MemoryClassInfo info(memoryObjectInfo, this, WebCoreMemoryTypes::CSS);
     info.addMember(m_mediaType, "mediaType");
     info.addMember(m_expressions, "expressions");
     info.addMember(m_serializationCache, "serializationCache");
 }
 
 }