Fix issue where we were not centering absolute nodes correctly when j…

…ustifying (facebook#41690)

Summary:
X-link: facebook/yoga#1489


Centering involves centering the margin box in the content box of the parent, and then getting the distance from the flex start edge of the parent to the child

Reviewed By: NickGerleman

Differential Revision: D51383625

packages/react-native/ReactCommon/yoga/yoga/algorithm/AbsoluteLayout.cpp

@@ -38,10 +38,21 @@ static void justifyAbsoluteChild(
     case Justify::Center:
     case Justify::SpaceAround:
     case Justify::SpaceEvenly:
+      const float parentContentBoxSize =
+          parent->getLayout().measuredDimension(dimension(mainAxis)) -
+          parent->getLayout().border(flexStartEdge(mainAxis)) -
+          parent->getLayout().border(flexEndEdge(mainAxis)) -
+          parent->getLayout().padding(flexStartEdge(mainAxis)) -
+          parent->getLayout().padding(flexEndEdge(mainAxis));
+      const float childOuterSize =
+          child->getLayout().measuredDimension(dimension(mainAxis)) +
+          child->getMarginForAxis(mainAxis, containingBlockWidth);
       child->setLayoutPosition(
-          (parent->getLayout().measuredDimension(dimension(mainAxis)) -
-           child->getLayout().measuredDimension(dimension(mainAxis))) /
-              2.0f,
+          (parentContentBoxSize - childOuterSize) / 2.0f +
+              parent->getLayout().border(flexStartEdge(mainAxis)) +
+              parent->getLayout().padding(flexStartEdge(mainAxis)) +
+              child->getFlexStartMargin(
+                  mainAxis, direction, containingBlockWidth),
           flexStartEdge(mainAxis));
       break;
   }