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

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 1c1eb5780f5380fa6fc7e183fc073d7bb97ed3fa..e02e1084570020698f58459c2b86e844aff54bfa 100644
--- a/Source/core/css/CSSComputedStyleDeclaration.cpp
+++ b/Source/core/css/CSSComputedStyleDeclaration.cpp
@@ -136,6 +136,7 @@ static const CSSPropertyID staticComputableProperties[] = {
     CSSPropertyHeight,
     CSSPropertyImageRendering,
     CSSPropertyIsolation,
+    CSSPropertyJustifyItems,
     CSSPropertyJustifySelf,
     CSSPropertyLeft,
     CSSPropertyLetterSpacing,
@@ -1554,9 +1555,11 @@ Node* CSSComputedStyleDeclaration::styledNode() const
     return m_node.get();
 }
 
-static PassRefPtrWillBeRawPtr<CSSValueList> valueForItemPositionWithOverflowAlignment(ItemPosition itemPosition, OverflowAlignment overflowAlignment)
+static PassRefPtrWillBeRawPtr<CSSValueList> valueForItemPositionWithOverflowAlignment(ItemPosition itemPosition, OverflowAlignment overflowAlignment, bool isLegacy)
 {
     RefPtrWillBeRawPtr<CSSValueList> result = CSSValueList::createSpaceSeparated();
+    if (isLegacy)
+        result->append(CSSPrimitiveValue::createIdentifier(CSSValueLegacy));
     result->append(CSSPrimitiveValue::create(itemPosition));
     if (itemPosition >= ItemPositionCenter && overflowAlignment != OverflowAlignmentDefault)
         result->append(CSSPrimitiveValue::create(overflowAlignment));
@@ -1886,7 +1889,7 @@ PassRefPtrWillBeRawPtr<CSSValue> CSSComputedStyleDeclaration::getPropertyCSSValu
         case CSSPropertyAlignContent:
             return cssValuePool().createValue(style->alignContent());
         case CSSPropertyAlignItems:
-            return valueForItemPositionWithOverflowAlignment(style->alignItems(), style->alignItemsOverflowAlignment());
+            return valueForItemPositionWithOverflowAlignment(style->alignItems(), style->alignItemsOverflowAlignment(), false);
         case CSSPropertyAlignSelf: {
             ItemPosition alignSelf = style->alignSelf();
             if (alignSelf == ItemPositionAuto) {
@@ -1896,7 +1899,7 @@ PassRefPtrWillBeRawPtr<CSSValue> CSSComputedStyleDeclaration::getPropertyCSSValu
                 else
                     alignSelf = ItemPositionStretch;
             }
-            return valueForItemPositionWithOverflowAlignment(alignSelf, style->alignSelfOverflowAlignment());
+            return valueForItemPositionWithOverflowAlignment(alignSelf, style->alignSelfOverflowAlignment(), false);
         }
         case CSSPropertyFlex:
             return valuesForShorthandProperty(flexShorthand());
@@ -2027,8 +2030,10 @@ PassRefPtrWillBeRawPtr<CSSValue> CSSComputedStyleDeclaration::getPropertyCSSValu
             return CSSPrimitiveValue::create(style->imageRendering());
         case CSSPropertyIsolation:
             return cssValuePool().createValue(style->isolation());
+        case CSSPropertyJustifyItems:
+            return valueForItemPositionWithOverflowAlignment(style->justifyItems(), style->justifyItemsOverflowAlignment(), style->justifyItemsIsLegacy());
         case CSSPropertyJustifySelf:
-            return valueForItemPositionWithOverflowAlignment(style->justifySelf(), style->justifySelfOverflowAlignment());
+            return valueForItemPositionWithOverflowAlignment(style->justifySelf(), style->justifySelfOverflowAlignment(), false);
         case CSSPropertyLeft:
             return valueForPositionOffset(*style, CSSPropertyLeft, renderer);
         case CSSPropertyLetterSpacing: