orphans and widows should be positive integer.

Source/core/css/CSSParser-in.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 2018 matching lines @@
     case CSSPropertyWebkitMarginStart:
     case CSSPropertyWebkitMarginEnd:
     case CSSPropertyWebkitMarginBefore:
     case CSSPropertyWebkitMarginAfter:
         if (id == CSSValueAuto)
             validPrimitive = true;
         else
             validPrimitive = (!id && validUnit(value, FLength | FPercent));
         break;
 
-    case CSSPropertyZIndex:              // auto | <integer> | inherit
-        if (id == CSSValueAuto) {
-            validPrimitive = true;
-            break;
-        }
-        /* nobreak */
     case CSSPropertyOrphans: // <integer> | inherit | auto (We've added support for auto for backwards compatibility)
     case CSSPropertyWidows: // <integer> | inherit | auto (Ditto)
         if (id == CSSValueAuto)
             validPrimitive = true;
         else
+            validPrimitive = (!id && validUnit(value, FPositiveInteger, HTMLQuirksMode));
+        break;
+
+    case CSSPropertyZIndex: // auto | <integer> | inherit
+        if (id == CSSValueAuto)
+            validPrimitive = true;
+        else
             validPrimitive = (!id && validUnit(value, FInteger, HTMLQuirksMode));
         break;
 
     case CSSPropertyLineHeight:
         return parseLineHeight(important);
     case CSSPropertyCounterIncrement:    // [ <identifier> <integer>? ]+ | none | inherit
         if (id != CSSValueNone)
             return parseCounter(propId, 1, important);
         validPrimitive = true;
         break;
@@ skipping 8396 matching lines @@
 {
     // 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");
 }
 
 }