Remove unused isValidNthToken function

Source/core/css/parser/CSSPropertyParser.cpp

 /*
  * Copyright (C) 2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Nicholas Shanks <webkit@nickshanks.com>
  * Copyright (C) 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2012 Adobe Systems Incorporated. All rights reserved.
  * Copyright (C) 2012 Intel Corporation. All rights reserved.
  *
@@ skipping 7568 matching lines @@
 {
     unsigned length = string.length();
     if (!length)
         return CSSValueInvalid;
     if (length > maxCSSValueKeywordLength)
         return CSSValueInvalid;
 
     return string.is8Bit() ? cssValueKeywordID(string.characters8(), length) : cssValueKeywordID(string.characters16(), length);
 }
 
-// FIXME: This has nothing to do with parsing properties
-bool isValidNthToken(const CSSParserString& token)
-{
-    // The tokenizer checks for the construct of an+b.
-    // However, since the {ident} rule precedes the {nth} rule, some of those
-    // tokens are identified as string literal. Furthermore we need to accept
-    // "odd" and "even" which does not match to an+b.
-    return equalIgnoringCase(token, "odd") || equalIgnoringCase(token, "even")
-        || equalIgnoringCase(token, "n") || equalIgnoringCase(token, "-n");
-}
-
 bool CSSPropertyParser::isSystemColor(int id)
 {
     return (id >= CSSValueActiveborder && id <= CSSValueWindowtext) || id == CSSValueMenu;
 }
 
 bool CSSPropertyParser::parseSVGValue(CSSPropertyID propId, bool important)
 {
     CSSParserValue* value = m_valueList->current();
     ASSERT(value);
 
@@ skipping 580 matching lines @@
         }
     }
 
     if (!list->length())
         return nullptr;
 
     return list.release();
 }
 
 } // namespace blink