Allow defining named grid lines on the grid element

Source/core/css/CSSParser.cpp

Index: Source/core/css/CSSParser.cpp
diff --git a/Source/core/css/CSSParser.cpp b/Source/core/css/CSSParser.cpp
index b720da65aceae3a078e9da9c50c457c691dbe648..37a59d9168dbc016b2405181334e317a86ff00e3 100644
--- a/Source/core/css/CSSParser.cpp
+++ b/Source/core/css/CSSParser.cpp
@@ -4634,7 +4634,18 @@ bool CSSParser::parseGridTrackList(CSSPropertyID propId, bool important)
     }
 
     RefPtr<CSSValueList> values = CSSValueList::createSpaceSeparated();
+    size_t currentLineNumber = 0;
     while (m_valueList->current()) {
+        while (m_valueList->current() && m_valueList->current()->unit == CSSPrimitiveValue::CSS_STRING) {
+            RefPtr<CSSPrimitiveValue> name = createPrimitiveStringValue(m_valueList->current());
+            values->append(name);
+            m_valueList->next();
+        }
+
+        // This allows trailing <string>* per the specification.
+        if (!m_valueList->current())
+            break;
+
         RefPtr<CSSPrimitiveValue> primitiveValue = parseGridTrackSize();
         if (!primitiveValue)
             return false;