[CSS Grid Layout] Adapting align-self, align-items and justify-self to the last CSS 3 spec.

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 d34ce94922e4e15fcff7e6cb129cc3f92f423e0b..2a787abbb71619f20f43cc80bedda0893f3d35ec 100644
--- a/Source/core/css/CSSComputedStyleDeclaration.cpp
+++ b/Source/core/css/CSSComputedStyleDeclaration.cpp
@@ -1556,6 +1556,17 @@ Node* CSSComputedStyleDeclaration::styledNode() const
     return m_node.get();
 }
 
+static ItemPosition resolveAlignmentAuto(ItemPosition position, Node* element)
+{
+    if (position != ItemPositionAuto)
+        return position;
+
+    bool isFlexOrGrid = element && element->computedStyle()
+        && element->computedStyle()->isDisplayFlexibleOrGridBox();
+
+    return isFlexOrGrid ? ItemPositionStretch : ItemPositionStart;
+}
+
 static PassRefPtrWillBeRawPtr<CSSValueList> valueForItemPositionWithOverflowAlignment(ItemPosition itemPosition, OverflowAlignment overflowAlignment, ItemPositionType positionType)
 {
     RefPtrWillBeRawPtr<CSSValueList> result = CSSValueList::createSpaceSeparated();
@@ -1886,18 +1897,9 @@ PassRefPtrWillBeRawPtr<CSSValue> CSSComputedStyleDeclaration::getPropertyCSSValu
         case CSSPropertyAlignContent:
             return cssValuePool().createValue(style->alignContent());
         case CSSPropertyAlignItems:
-            return valueForItemPositionWithOverflowAlignment(style->alignItems(), style->alignItemsOverflowAlignment(), NonLegacyPosition);
-        case CSSPropertyAlignSelf: {
-            ItemPosition alignSelf = style->alignSelf();
-            if (alignSelf == ItemPositionAuto) {
-                Node* parent = styledNode->parentNode();
-                if (parent && parent->computedStyle())
-                    alignSelf = parent->computedStyle()->alignItems();
-                else
-                    alignSelf = ItemPositionStretch;
-            }
-            return valueForItemPositionWithOverflowAlignment(alignSelf, style->alignSelfOverflowAlignment(), NonLegacyPosition);
-        }
+            return valueForItemPositionWithOverflowAlignment(resolveAlignmentAuto(style->alignItems(), styledNode), style->alignItemsOverflowAlignment(), NonLegacyPosition);
+        case CSSPropertyAlignSelf:
+            return valueForItemPositionWithOverflowAlignment(resolveAlignmentAuto(style->alignSelf(), styledNode->parentNode()), style->alignSelfOverflowAlignment(), NonLegacyPosition);
         case CSSPropertyFlex:
             return valuesForShorthandProperty(flexShorthand());
         case CSSPropertyFlexBasis:
@@ -2061,47 +2063,10 @@ PassRefPtrWillBeRawPtr<CSSValue> CSSComputedStyleDeclaration::getPropertyCSSValu
             return CSSPrimitiveValue::create(style->imageRendering());
         case CSSPropertyIsolation:
             return cssValuePool().createValue(style->isolation());
-        case CSSPropertyJustifyItems: {
-            // FIXME: I would like this to be tested; is not possible with a layout test but it
-            // should be possible using a method similar to https://codereview.chromium.org/351973004
-            ItemPosition justifyItems = style->justifyItems();
-            ItemPositionType positionType = style->justifyItemsPositionType();
-            if (justifyItems == ItemPositionAuto) {
-                Node* parent = styledNode->parentNode();
-                // If the inherited value of justify-items includes the legacy keyword, 'auto'
-                // computes to the the inherited value.
-                if (parent && parent->computedStyle() && parent->computedStyle()->justifyItemsPositionType()) {
-                    justifyItems = parent->computedStyle()->justifyItems();
-                    positionType = parent->computedStyle()->justifyItemsPositionType();
-                // Otherwise, auto computes to:
-                } else if (style->isDisplayFlexibleOrGridBox()) {
-                    // 'stretch' for flex containers and grid containers.
-                    justifyItems = ItemPositionStretch;
-                } else {
-                    // 'start' for everything else.
-                    justifyItems = ItemPositionStart;
-                }
-            }
-            return valueForItemPositionWithOverflowAlignment(justifyItems, style->justifyItemsOverflowAlignment(), positionType);
-        }
-        case CSSPropertyJustifySelf: {
-            // FIXME: I would like this to be tested; is not possible with a layout test but it
-            // should be possible using a method similar to https://codereview.chromium.org/351973004
-            ItemPosition justifySelf = style->justifySelf();
-            if (justifySelf == ItemPositionAuto) {
-                // The auto keyword computes to stretch on absolutely-positioned elements,
-                if (style->position() == AbsolutePosition) {
-                    justifySelf = ItemPositionStretch;
-                } else {
-                    // and to the computed value of justify-items on the parent (minus
-                    // any legacy keywords) on all other boxes.
-                    Node* parent = styledNode->parentNode();
-                    if (parent && parent->computedStyle())
-                        justifySelf = parent->computedStyle()->justifyItems();
-                }
-            }
-            return valueForItemPositionWithOverflowAlignment(justifySelf, style->justifySelfOverflowAlignment(), NonLegacyPosition);
-        }
+        case CSSPropertyJustifyItems:
+            return valueForItemPositionWithOverflowAlignment(resolveAlignmentAuto(style->justifyItems(), styledNode), style->justifyItemsOverflowAlignment(), style->justifyItemsPositionType());
+        case CSSPropertyJustifySelf:
+            return valueForItemPositionWithOverflowAlignment(resolveAlignmentAuto(style->justifySelf(), styledNode->parentNode()), style->justifySelfOverflowAlignment(), NonLegacyPosition);
         case CSSPropertyLeft:
             return valueForPositionOffset(*style, CSSPropertyLeft, renderer);
         case CSSPropertyLetterSpacing: