Seal RootShadowNode just before it is promoted (#39355)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/39355

changelog: [internal]

We want to seal node just before it is promoted.

Reviewed By: javache, NickGerleman

Differential Revision: D49054011

fbshipit-source-id: 92550c13280c68bf66d505872d86d775cf115f5d

packages/react-native/ReactCommon/react/renderer/mounting/ShadowTree.cpp

@@ -371,9 +371,6 @@ CommitStatus ShadowTree::tryCommit(
   telemetry.unsetAsThreadLocal();
   telemetry.didLayout(affectedLayoutableNodes.size());
 
-  // Seal the shadow node so it can no longer be mutated
-  newRootShadowNode->sealRecursive();
-
   {
     // Updating `currentRevision_` in unique manner if it hasn't changed.
     std::unique_lock lock(commitMutex_);
@@ -409,6 +406,9 @@ CommitStatus ShadowTree::tryCommit(
     telemetry.didCommit();
     telemetry.setRevisionNumber(static_cast<int>(newRevisionNumber));
 
+    // Seal the shadow node so it can no longer be mutated
+    newRootShadowNode->sealRecursive();
+
     newRevision = ShadowTreeRevision{
         std::move(newRootShadowNode), newRevisionNumber, telemetry};