[CSS Grid Layout] Add GridSpan::iterator

Source/core/css/parser/CSSPropertyParser.cpp

Index: Source/core/css/parser/CSSPropertyParser.cpp
diff --git a/Source/core/css/parser/CSSPropertyParser.cpp b/Source/core/css/parser/CSSPropertyParser.cpp
index 4b3b4acb72fba29fb124eb6843920f22f6f6e976..6448acf4ade86814fb1d4cc0d5b827df751cf4cd 100644
--- a/Source/core/css/parser/CSSPropertyParser.cpp
+++ b/Source/core/css/parser/CSSPropertyParser.cpp
@@ -3916,7 +3916,7 @@ bool CSSPropertyParser::parseGridTemplateAreasRow(NamedGridAreaMap& gridAreaMap,
 
             // The following checks test that the grid area is a single filled-in rectangle.
             // 1. The new row is adjacent to the previously parsed row.
-            if (rowCount != gridCoordinate.rows.resolvedFinalPosition.toInt() + 1)
+            if (rowCount != gridCoordinate.rows.resolvedFinalPosition.next().toInt())
                 return false;
 
             // 2. The new area starts at the same position as the previously parsed area.