[Sync] ModelTypeWorker should delete tracker for entity deleted on the server

components/sync/test/engine/mock_model_type_processor.h

Index: components/sync/test/engine/mock_model_type_processor.h
diff --git a/components/sync/test/engine/mock_model_type_processor.h b/components/sync/test/engine/mock_model_type_processor.h
index bc0bb78558f3a3af52f25024f802612d8c67a151..632d189e4a67d67c49f8cdbf9da76303d8e8042a 100644
--- a/components/sync/test/engine/mock_model_type_processor.h
+++ b/components/sync/test/engine/mock_model_type_processor.h
@@ -10,6 +10,7 @@
 
 #include <map>
 #include <memory>
+#include <set>
 #include <string>
 #include <vector>
 
@@ -140,6 +141,10 @@ class MockModelTypeProcessor : public ModelTypeProcessor {
   std::map<const std::string, int64_t> base_versions_;
   std::map<const std::string, std::string> assigned_ids_;
 
+  // Set of tag hashes which were deleted with DeleteRequest but haven't yet
+  // been confirmed by the server with OnCommitCompleted.
+  std::set<std::string> pending_deleted_hashes_;
+
   // Callback which will be call during disconnection
   DisconnectCallback disconnect_callback_;