[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 472fa870517b80bc94de995c07a765925dc219ce..a288b1bfb0d2691ae2f0ee8626a2e65c06f6c0db 100644
--- a/Source/core/css/CSSComputedStyleDeclaration.cpp
+++ b/Source/core/css/CSSComputedStyleDeclaration.cpp
@@ -1891,17 +1891,8 @@ PassRefPtrWillBeRawPtr<CSSValue> CSSComputedStyleDeclaration::getPropertyCSSValu
             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);
-        }
+        case CSSPropertyAlignSelf:
+            return valueForItemPositionWithOverflowAlignment(style->alignSelf(), style->alignSelfOverflowAlignment(), NonLegacyPosition);
         case CSSPropertyFlex:
             return valuesForShorthandProperty(flexShorthand());
         case CSSPropertyFlexBasis:
@@ -2065,47 +2056,10 @@ 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(style->justifyItems(), style->justifyItemsOverflowAlignment(), style->justifyItemsPositionType());
+        case CSSPropertyJustifySelf:
+            return valueForItemPositionWithOverflowAlignment(style->justifySelf(), style->justifySelfOverflowAlignment(), NonLegacyPosition);
         case CSSPropertyLeft:
             return valueForPositionOffset(*style, CSSPropertyLeft, renderer);
         case CSSPropertyLetterSpacing: