[Sync] USS: Filter out tombstones for initial sync.

components/sync/engine_impl/uss_migrator.cc

Index: components/sync/engine_impl/uss_migrator.cc
diff --git a/components/sync/engine_impl/uss_migrator.cc b/components/sync/engine_impl/uss_migrator.cc
index b853cb2faa7d448e2949772d81188d97607cf8cb..91db78f3470573c4f95d1e2ba53e0616a114d473 100644
--- a/components/sync/engine_impl/uss_migrator.cc
+++ b/components/sync/engine_impl/uss_migrator.cc
@@ -103,8 +103,11 @@ bool MigrateDirectoryDataWithBatchSize(ModelType type,
         worker->AbortMigration();
         return false;
       }
-      entity_ptrs.push_back(entity.get());
-      entities.push_back(std::move(entity));
+      // Ignore tombstones; they are not included for initial GetUpdates.
+      if (!entity->deleted()) {
+        entity_ptrs.push_back(entity.get());
+        entities.push_back(std::move(entity));
+      }
     }
 
     worker->ProcessGetUpdatesResponse(progress, context, entity_ptrs, nullptr);