[CSS Grid] Introduce an explicit type for resolved grid positions

Source/core/css/CSSGridTemplateValue.cpp

Index: Source/core/css/CSSGridTemplateValue.cpp
diff --git a/Source/core/css/CSSGridTemplateValue.cpp b/Source/core/css/CSSGridTemplateValue.cpp
index d1ad1d8d056589c1e09ff10b8b2d7489f5276c09..f8114026a519927d9efff20198d5650011e1408f 100644
--- a/Source/core/css/CSSGridTemplateValue.cpp
+++ b/Source/core/css/CSSGridTemplateValue.cpp
@@ -52,14 +52,14 @@ static String stringForPosition(const NamedGridAreaMap& gridAreaMap, size_t row,
     NamedGridAreaMap::const_iterator end = gridAreaMap.end();
     for (NamedGridAreaMap::const_iterator it = gridAreaMap.begin(); it != end; ++it) {
         const GridCoordinate& coordinate = it->value;
-        if (row >= coordinate.rows.initialPositionIndex && row <= coordinate.rows.finalPositionIndex)
+        if (row >= coordinate.rows.initialPositionIndex.integerPosition() && row <= coordinate.rows.finalPositionIndex.integerPosition())
             candidates.append(it->key);
     }
 
     end = gridAreaMap.end();
     for (NamedGridAreaMap::const_iterator it = gridAreaMap.begin(); it != end; ++it) {
         const GridCoordinate& coordinate = it->value;
-        if (column >= coordinate.columns.initialPositionIndex && column <= coordinate.columns.finalPositionIndex && candidates.contains(it->key))
+        if (column >= coordinate.columns.initialPositionIndex.integerPosition() && column <= coordinate.columns.finalPositionIndex.integerPosition() && candidates.contains(it->key))
             return it->key;
     }