Changed new_cow_size var type to auto to prevent overflow.

Test: tested compilation
Change-Id: Ic40eeb3a82d0d15bcbff85910c4260542c949513
diff --git a/payload_consumer/delta_performer.cc b/payload_consumer/delta_performer.cc
index 5754cae..367dedc 100644
--- a/payload_consumer/delta_performer.cc
+++ b/payload_consumer/delta_performer.cc
@@ -474,7 +474,7 @@
       manifest_.mutable_dynamic_partition_metadata()
           ->set_vabc_compression_param("none");
       for (auto& partition : *manifest_.mutable_partitions()) {
-        int new_cow_size = partition.new_partition_info().size();
+        auto new_cow_size = partition.new_partition_info().size();
         for (const auto& operation : partition.merge_operations()) {
           if (operation.type() == CowMergeOperation::COW_COPY) {
             new_cow_size -=