Potentially fix seg fault when replace YogaLayoutableShadowNodes (fac…

…ebook#47689)

Summary:
Pull Request resolved: facebook#47689

We were seeing some segfaults from trying to access `display_` in Yoga's `replaceChild` function. Some memory debugging helped identify this was a use-after-free error and NickGerleman suggested we try swapping these lines. Logic being the shared_ptr of YogaLayoutableShadowNode is replaced right before we go and replace its yoga node in the yoga tree. If this is the last shared_ptr holding this node we will delete this object and thus the yoga node with it. We do not need to do this first, so let's swap the lines.

Changelog: [Internal]

Reviewed By: NickGerleman

Differential Revision: D66142356

fbshipit-source-id: 8fd835346edc91e045ed2ee8945a95af21c47556

packages/react-native/ReactCommon/react/renderer/components/view/YogaLayoutableShadowNode.cpp

@@ -300,13 +300,13 @@ void YogaLayoutableShadowNode::replaceChild(
     // Both children are layoutable, replace the old one with the new one
     react_native_assert(layoutableNewChild->yogaNode_.getOwner() == nullptr);
     layoutableNewChild->yogaNode_.setOwner(&yogaNode_);
-    *oldChildIter = layoutableNewChild;
     yogaNode_.replaceChild(&layoutableNewChild->yogaNode_, oldChildIndex);
+    *oldChildIter = layoutableNewChild;
   } else {
     // Layoutable child replaced with non layoutable child. Remove the previous
     // child from the layoutable children list.
-    yogaLayoutableChildren_.erase(oldChildIter);
     yogaNode_.removeChild(oldChildIndex);
+    yogaLayoutableChildren_.erase(oldChildIter);
   }
 
   ensureYogaChildrenLookFine();