[Sync] Add a sanity integration test for USS.

components/sync/engine_impl/worker_entity_tracker.h

Index: components/sync/engine_impl/worker_entity_tracker.h
diff --git a/components/sync/engine_impl/worker_entity_tracker.h b/components/sync/engine_impl/worker_entity_tracker.h
index 354502ad18eb0235a5fc83e04d96566303a0c8c0..1eea4f4356b1950d021f2809c5aee09f4dc8b5fd 100644
--- a/components/sync/engine_impl/worker_entity_tracker.h
+++ b/components/sync/engine_impl/worker_entity_tracker.h
@@ -72,6 +72,9 @@ class WorkerEntityTracker {
   // Clears the encrypted update. Allows us to resume regular commit behavior.
   void ClearEncryptedUpdate();
 
+  const std::string& id() const { return id_; }
+  const std::string& client_tag_hash() const { return client_tag_hash_; }
+
  private:
   // Checks if the current state indicates a conflict.
   //