Add support for parsing <grid-line> that includes a 'span'

Source/core/css/CSSComputedStyleDeclaration.cpp

Index: Source/core/css/CSSComputedStyleDeclaration.cpp
diff --git a/Source/core/css/CSSComputedStyleDeclaration.cpp b/Source/core/css/CSSComputedStyleDeclaration.cpp
index bf981f457a08e0e8d998cdb1b1724d5fc0c5b796..97ddfd692bcb5012d2b2281d51c089062577b6ba 100644
--- a/Source/core/css/CSSComputedStyleDeclaration.cpp
+++ b/Source/core/css/CSSComputedStyleDeclaration.cpp
@@ -1053,7 +1053,13 @@ static PassRefPtr<CSSValue> valueForGridPosition(const GridPosition& position)
     if (position.isAuto())
         return cssValuePool().createIdentifierValue(CSSValueAuto);
 
-    return cssValuePool().createValue(position.integerPosition(), CSSPrimitiveValue::CSS_NUMBER);
+    if (position.isInteger())
+        return cssValuePool().createValue(position.integerPosition(), CSSPrimitiveValue::CSS_NUMBER);
+
+    RefPtr<CSSValueList> list = CSSValueList::createSpaceSeparated();
+    list->append(cssValuePool().createIdentifierValue(CSSValueSpan));
+    list->append(cssValuePool().createValue(position.spanPosition(), CSSPrimitiveValue::CSS_NUMBER));
+    return list;
 }
 static PassRefPtr<CSSValue> createTransitionPropertyValue(const Animation* animation)
 {