message: Reduce memory wasted by GCS cache by shrinking buffer capacity, after a cache fill completes.
diff: @@ -131,6 +131,7 @@ Status FileBlockCache::MaybeFetch(const Key& key,
  block->mu.lock(); // Reacquire the lock immediately afterwards
  if (status.ok()) {
  block->data.resize(bytes_transferred, 0);
  + block->data.shrink_to_fit();
  downloaded_block = true;
  block->state = FetchState::FINISHED;
  } else {
  