Compare :lang value case-insensitive in ASCII range

Source/core/css/SelectorChecker.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. All rights reserved.
@@ skipping 946 matching lines @@
     case CSSSelector::PseudoRoot:
         return element == element.document().documentElement();
     case CSSSelector::PseudoLang:
         {
             AtomicString value;
             if (element.isVTTElement())
                 value = toVTTElement(element).language();
             else
                 value = element.computeInheritedLanguage();
             const AtomicString& argument = selector.argument();
-            if (value.isEmpty() || !value.startsWith(argument, TextCaseInsensitive))
+            if (value.isEmpty() || !startsWithIgnoringASCIICase(value, argument))
                 break;
             if (value.length() != argument.length() && value[argument.length()] != '-')
                 break;
             return true;
         }
     case CSSSelector::PseudoFullScreen:
         // While a Document is in the fullscreen state, and the document's current fullscreen
         // element is an element in the document, the 'full-screen' pseudoclass applies to
         // that element. Also, an <iframe>, <object> or <embed> element whose child browsing
         // context's Document is in the fullscreen state has the 'full-screen' pseudoclass applied.
@@ skipping 222 matching lines @@
 }
 
 bool SelectorChecker::matchesFocusPseudoClass(const Element& element)
 {
     if (InspectorInstrumentation::forcePseudoState(const_cast<Element*>(&element), CSSSelector::PseudoFocus))
         return true;
     return element.focused() && isFrameFocused(element);
 }
 
 }