Fix memory leak in Sync FakeServerEntity

sync/test/fake_server/fake_server.cc

Index: sync/test/fake_server/fake_server.cc
diff --git a/sync/test/fake_server/fake_server.cc b/sync/test/fake_server/fake_server.cc
index 854eabec6c5b8207afac3d95b00df2c23af78219..ea4abfd7cf55812003e8e7d8ccc47bee2bc5024e 100644
--- a/sync/test/fake_server/fake_server.cc
+++ b/sync/test/fake_server/fake_server.cc
@@ -288,7 +288,7 @@ bool FakeServer::HandleGetUpdatesRequest(
     FakeServerEntity* entity = it->second;
     if (sieve->ClientWantsItem(entity)) {
       sync_pb::SyncEntity* response_entity = response->add_entries();
-      response_entity->CopyFrom(*(entity->SerializeAsProto()));
+      entity->SerializeAsProto(response_entity);
       max_response_version = std::max(max_response_version,
                                       response_entity->version());