[CSS Grid Layout] Implement 'justify-items' parsing

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 4c3d25149345a119e48b66d79f01144bdcbaeba9..d0ba6240a22e1ddd685fbbdd92387b5e645f1179 100644
--- a/Source/core/css/parser/CSSPropertyParser.cpp
+++ b/Source/core/css/parser/CSSPropertyParser.cpp
@@ -1199,6 +1199,18 @@ bool CSSPropertyParser::parseValue(CSSPropertyID propId, bool important)
             return false;
 
         return parseItemPositionOverflowPosition(propId, important);
+
+    case CSSPropertyJustifyItems:
+        if (!RuntimeEnabledFeatures::cssGridLayoutEnabled())
+            return false;
+
+        if (!parseLegacyPosition(propId, important)) {
+            m_valueList->setCurrentIndex(0);
+            return parseItemPositionOverflowPosition(propId, important);
+        }
+
+        return true;
+
     case CSSPropertyGridAutoColumns:
     case CSSPropertyGridAutoRows:
         if (!RuntimeEnabledFeatures::cssGridLayoutEnabled())
@@ -4133,6 +4145,25 @@ static bool isItemPositionKeyword(CSSValueID id)
         || id == CSSValueFlexEnd || id == CSSValueLeft || id == CSSValueRight;
 }
 
+bool CSSPropertyParser::parseLegacyPosition(CSSPropertyID propId, bool important)
+{
+    // [ legacy && [ left | right | center ]
+
+    CSSParserValue* value = m_valueList->current();
+    if (!value || value->id != CSSValueLegacy || !(value = m_valueList->next()))
+        return false;
+
+    if (value->id == CSSValueCenter || value->id == CSSValueLeft || value->id == CSSValueRight) {
+        if (m_valueList->next())
+            return false;
+
+        addProperty(propId, createPrimitiveValuePair(cssValuePool().createIdentifierValue(CSSValueLegacy), cssValuePool().createIdentifierValue(value->id)), important);
+        return true;
+    }
+
+    return false;
+}
+
 bool CSSPropertyParser::parseItemPositionOverflowPosition(CSSPropertyID propId, bool important)
 {
     // auto | baseline | stretch | [<item-position> && <overflow-position>? ]
@@ -4140,6 +4171,8 @@ bool CSSPropertyParser::parseItemPositionOverflowPosition(CSSPropertyID propId,
     // <overflow-position> = true | safe
 
     CSSParserValue* value = m_valueList->current();
+    if (!value)
+        return false;
 
     if (value->id == CSSValueAuto || value->id == CSSValueBaseline || value->id == CSSValueStretch) {
         if (m_valueList->next())