Fix memory leak in Sync FakeServerEntity

sync/test/fake_server/tombstone_entity.cc

Index: sync/test/fake_server/tombstone_entity.cc
diff --git a/sync/test/fake_server/tombstone_entity.cc b/sync/test/fake_server/tombstone_entity.cc
index e68deb3ebb9b12b8547b5af753f0b7565e3c9472..801690fe719583013c75a5da607a5f71ad8ae003 100644
--- a/sync/test/fake_server/tombstone_entity.cc
+++ b/sync/test/fake_server/tombstone_entity.cc
@@ -32,14 +32,11 @@ string TombstoneEntity::GetParentId() const {
   return string();
 }
 
-sync_pb::SyncEntity* TombstoneEntity::SerializeAsProto() {
-  sync_pb::SyncEntity* sync_entity = new sync_pb::SyncEntity();
-  FakeServerEntity::SerializeBaseProtoFields(sync_entity);
+void TombstoneEntity::SerializeAsProto(sync_pb::SyncEntity* proto) {
+  FakeServerEntity::SerializeBaseProtoFields(proto);
 
-  sync_pb::EntitySpecifics* specifics = sync_entity->mutable_specifics();
+  sync_pb::EntitySpecifics* specifics = proto->mutable_specifics();
   AddDefaultFieldValue(FakeServerEntity::GetModelType(), specifics);
-
-  return sync_entity;
 }
 
 bool TombstoneEntity::IsDeleted() const {