message: [tstring] Avoid temporary std::string creation in MergeBundles().
diff: @@ -716,7 +716,7 @@ Status MergeBundles(Env* env, gtl::ArraySlice<tstring> prefixes,
  VLOG(1) << "Merged bundles to:" << merged_prefix;
  // Cleanup: best effort based and ignores errors.
  - for (const string& prefix : prefixes) {
  + for (const tstring& prefix : prefixes) {
  env->DeleteFile(MetaFilename(prefix)).IgnoreError();
  }
  return status;
  