Read the default min-width value from the UA style sheets

Source/core/dom/Document.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 3012 matching lines @@
     }
 }
 
 bool Document::shouldMergeWithLegacyDescription(ViewportDescription::Type origin)
 {
     return settings() && settings()->viewportMetaMergeContentQuirk() && m_legacyViewportDescription.isMetaViewportType() && m_legacyViewportDescription.type == origin;
 }
 
 void Document::setViewportDescription(const ViewportDescription& viewportDescription)
 {
+    // The UA-defined min-width is used by the processing of legacy meta tags.
+    if (!viewportDescription.isSpecifiedByAuthor())
+        m_viewportDefaultMinWidth = viewportDescription.minWidth;
+
     if (viewportDescription.isLegacyViewportType()) {
         if (settings() && !settings()->viewportMetaEnabled())
             return;
 
         m_legacyViewportDescription = viewportDescription;
 
         // When no author style for @viewport is present, and a meta tag for defining
         // the viewport is, apply the meta tag viewport instead of the UA styles.
         if (m_viewportDescription.type == ViewportDescription::AuthorStyleSheet)
             return;
@@ skipping 2448 matching lines @@
 }
 
 void Document::invalidateNodeListCaches(const QualifiedName* attrName)
 {
     HashSet<LiveNodeListBase*>::iterator end = m_listsInvalidatedAtDocument.end();
     for (HashSet<LiveNodeListBase*>::iterator it = m_listsInvalidatedAtDocument.begin(); it != end; ++it)
         (*it)->invalidateCache(attrName);
 }
 
 } // namespace WebCore