Serialize zIndex as an integer

Source/core/css/ComputedStyleCSSValueMapping.cpp

 /*
  * Copyright (C) 2004 Zack Rusin <zack@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007 Nicholas Shanks <webkit@nickshanks.com>
  * Copyright (C) 2011 Sencha, Inc. All rights reserved.
  * Copyright (C) 2015 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ skipping 2061 matching lines @@
             valueList->append(cssValuePool().createIdentifierValue(discretionaryLigaturesState == FontDescription::DisabledLigaturesState ? CSSValueNoDiscretionaryLigatures : CSSValueDiscretionaryLigatures));
         if (historicalLigaturesState != FontDescription::NormalLigaturesState)
             valueList->append(cssValuePool().createIdentifierValue(historicalLigaturesState == FontDescription::DisabledLigaturesState ? CSSValueNoHistoricalLigatures : CSSValueHistoricalLigatures));
         if (contextualLigaturesState != FontDescription::NormalLigaturesState)
             valueList->append(cssValuePool().createIdentifierValue(contextualLigaturesState == FontDescription::DisabledLigaturesState ? CSSValueNoContextual : CSSValueContextual));
         return valueList;
     }
     case CSSPropertyZIndex:
         if (style.hasAutoZIndex())
             return cssValuePool().createIdentifierValue(CSSValueAuto);
-        return cssValuePool().createValue(style.zIndex(), CSSPrimitiveValue::CSS_NUMBER);
+        return cssValuePool().createValue(style.zIndex(), CSSPrimitiveValue::CSS_INTEGER);
     case CSSPropertyZoom:
         return cssValuePool().createValue(style.zoom(), CSSPrimitiveValue::CSS_NUMBER);
     case CSSPropertyBoxSizing:
         if (style.boxSizing() == CONTENT_BOX)
             return cssValuePool().createIdentifierValue(CSSValueContentBox);
         return cssValuePool().createIdentifierValue(CSSValueBorderBox);
     case CSSPropertyWebkitAppRegion:
         return cssValuePool().createIdentifierValue(style.getDraggableRegionMode() == DraggableRegionDrag ? CSSValueDrag : CSSValueNoDrag);
     case CSSPropertyAnimationDelay:
         return valueForAnimationDelay(style.animations());
@@ skipping 598 matching lines @@
     case CSSPropertyAll:
         return nullptr;
     default:
         break;
     }
     ASSERT_NOT_REACHED();
     return nullptr;
 }
 
 }