message: [Eager] In default_runner, avoid unnecessary copy of the closure to be run.
  This change fixes a ClangTidy warning in kernel_and_device.cc. However, the runner is almost always non-null, so the performance impact of this change is likely to be negligible.
diff: @@ -74,7 +74,7 @@ std::function<void(std::function<void()>)>* KernelAndDevice::get_runner()
  } else {
  static auto* default_runner =
  new std::function<void(std::function<void()>)>(
  - [](std::function<void()> f) { f(); });
  + [](const std::function<void()>& f) { f(); });
  return default_runner;
  }
  }
  