Serialize zIndex as an integer

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 842 matching lines @@
 
     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 = validUnit(value, FPositiveInteger);
         break;
 
     case CSSPropertyZIndex: // auto | <integer> | inherit
-        if (id == CSSValueAuto)
+        if (id == CSSValueAuto) {
             validPrimitive = true;
-        else
-            validPrimitive = validUnit(value, FInteger);
+        } else if (validUnit(value, FInteger)) {
+            addProperty(propId, cssValuePool().createValue(value->fValue, CSSPrimitiveValue::CSS_INTEGER), important);
+            return true;
+        }
         break;
 
     case CSSPropertyLineHeight:
         parsedValue = parseLineHeight();
         break;
     case CSSPropertyCounterIncrement:
         if (id == CSSValueNone)
             validPrimitive = true;
         else
             parsedValue = parseCounter(1);
@@ skipping 7369 matching lines @@
         }
     }
 
     if (!list->length())
         return nullptr;
 
     return list.release();
 }
 
 } // namespace blink