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

Source/core/dom/ViewportDescription.h

 /*
  * 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 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2012-2013 Intel Corporation. All rights reserved.
  *
@@ skipping 52 matching lines @@
         , zoom(ValueAuto)
         , minZoom(ValueAuto)
         , maxZoom(ValueAuto)
         , userZoom(ValueAuto)
         , orientation(ValueAuto)
         , deprecatedTargetDensityDPI(ValueAuto)
     {
     }
 
     // All arguments are in CSS units.
-    PageScaleConstraints resolve(const FloatSize& initialViewportSize) const;
+    PageScaleConstraints resolve(const FloatSize& initialViewportSize, Length legacyFallbackWidth) const;
 
     Length minWidth;
     Length maxWidth;
     Length minHeight;
     Length maxHeight;
     float zoom;
     float minZoom;
     float maxZoom;
     float userZoom;
     float orientation;
@@ skipping 25 matching lines @@
     bool isSpecifiedByAuthor() const { return type != UserAgentStyleSheet; }
 
 private:
     enum Direction { Horizontal, Vertical };
     static float resolveViewportLength(const Length&, const FloatSize& initialViewportSize, Direction);
 };
 
 } // namespace WebCore
 
 #endif // ViewportDescription_h