orphans and widows should be positive integer.

Source/core/css/CSSParser-in.cpp

Index: Source/core/css/CSSParser-in.cpp
diff --git a/Source/core/css/CSSParser-in.cpp b/Source/core/css/CSSParser-in.cpp
index 7b540fd7b14933d06d2f785664449768abe7f452..8be6c7b03009b9fec83c448242f8318fcb95c5e5 100755
--- a/Source/core/css/CSSParser-in.cpp
+++ b/Source/core/css/CSSParser-in.cpp
@@ -2036,17 +2036,18 @@ bool CSSParser::parseValue(CSSPropertyID propId, bool important)
             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;