[CSS Grid Layout] Remove stack from grid-auto-flow syntax

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 3798 matching lines @@
     }
 
     if (!rowCount || !columnCount)
         return nullptr;
 
     return CSSGridTemplateAreasValue::create(gridAreaMap, rowCount, columnCount);
 }
 
 PassRefPtrWillBeRawPtr<CSSValue> CSSPropertyParser::parseGridAutoFlow(CSSParserValueList& list)
 {
-    // [ row | column ] && dense? | stack && [ row | column ]?
+    // [ row | column ] || dense
     ASSERT(RuntimeEnabledFeatures::cssGridLayoutEnabled());
 
     CSSParserValue* value = list.current();
     if (!value)
         return nullptr;
 
     RefPtrWillBeRawPtr<CSSValueList> parsedValues = CSSValueList::createSpaceSeparated();
 
     // First parameter.
     CSSValueID firstId = value->id;
-    if (firstId != CSSValueRow && firstId != CSSValueColumn && firstId != CSSValueDense && firstId != CSSValueStack)
+    if (firstId != CSSValueRow && firstId != CSSValueColumn && firstId != CSSValueDense)
         return nullptr;
     parsedValues->append(cssValuePool().createIdentifierValue(firstId));
 
     // Second parameter, if any.
     value = list.next();
-    if (!value && firstId == CSSValueDense)
-        return nullptr;
-
     if (value) {
         switch (firstId) {
         case CSSValueRow:
         case CSSValueColumn:
-            if (value->id != CSSValueDense && value->id != CSSValueStack)
+            if (value->id != CSSValueDense)
                 return parsedValues;
             break;
         case CSSValueDense:
-        case CSSValueStack:
             if (value->id != CSSValueRow && value->id != CSSValueColumn)
                 return parsedValues;
             break;
         default:
             return parsedValues;
         }
         parsedValues->append(cssValuePool().createIdentifierValue(value->id));
         list.next();
     }
 
@@ skipping 4741 matching lines @@
         }
     }
 
     if (!list->length())
         return nullptr;
 
     return list.release();
 }
 
 } // namespace blink