[Sync] Add HasChildren() function and use it instead of GetFirstChildId()

chrome/browser/sync/glue/password_model_associator.cc

Index: chrome/browser/sync/glue/password_model_associator.cc
diff --git a/chrome/browser/sync/glue/password_model_associator.cc b/chrome/browser/sync/glue/password_model_associator.cc
index fecea089a7cc03d6620b9795dbcbe3ced2222279..519b7296fb5e032e4696c2fcb4863ff954830baf 100644
--- a/chrome/browser/sync/glue/password_model_associator.cc
+++ b/chrome/browser/sync/glue/password_model_associator.cc
@@ -209,7 +209,7 @@ bool PasswordModelAssociator::SyncModelHasUserCreatedNodes(bool* has_nodes) {
 
   // The sync model has user created nodes if the password folder has any
   // children.
-  *has_nodes = sync_api::kInvalidId != password_node.GetFirstChildId();
+  *has_nodes = password_node.HasChildren();
   return true;
 }