selectLocationState function appears to cause render without state change

[ghost]

I noticed the other day that my entire app was being rendered more frequently than expected. I eventually tracked this down to the Router component, which seemed to be rendering on every new action. I think the cause of this may be the selectLocationState function described in the docs, which invokes toJS on the routing state subtree. As I understand it, this creates a new JavaScript object every time the function is called, which is not equal to the previous object even if it contains the same data, causing React to re-render the Router. I tried replacing this with a memoized function that would return an identical object for the same state, and this appeared to fix the problem:

const history = syncHistoryWithStore(browserHistory, store, {
  selectLocationState: (function () {
    let prevState;
    let prevStateJS;
    function selectLocationStateHelper(state) {
      const newState = state.get('routing');
      if (!newState.equals(prevState)) {
        prevState = newState;
        prevStateJS = newState.toJS();
      }
      return prevStateJS;
    }
    return selectLocationStateHelper;
  }()),
});

Does it make sense to do something along these lines?

[gajus]

Refer to https://github.com/gajus/redux-immutable/pull/33.