[B4B-D] Add check in `IsParentFolderManaged()`

Add a CHECK if `PermanentFolderType::kManagedNode` is used as a
parameter to `IsParentFolderManaged()`, that a managed permanent node
exists.

Bug: 369304373
Change-Id: I8f913c961d11d9a75ca7256afa5f837cf7a28865
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5928673
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Commit-Queue: Monica Basta <msalama@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1368648}
diff --git a/chrome/browser/bookmarks/bookmark_merged_surface_service.cc b/chrome/browser/bookmarks/bookmark_merged_surface_service.cc
index 4f629ad..b6890cfa 100644
--- a/chrome/browser/bookmarks/bookmark_merged_surface_service.cc
+++ b/chrome/browser/bookmarks/bookmark_merged_surface_service.cc
@@ -189,7 +189,12 @@
   if (parent.HoldsNonPermanentFolder()) {
     return IsNodeManaged(parent.as_non_permanent_folder());
   }
-  return parent.as_permanent_folder() == PermanentFolderType::kManagedNode;
+
+  if (parent.as_permanent_folder() == PermanentFolderType::kManagedNode) {
+    CHECK(managed_permanent_node());
+    return true;
+  }
+  return false;
 }
 
 bool BookmarkMergedSurfaceService::IsNodeManaged(