validateState () {
    if (this.cachedStates) {
      this.setState(this.cachedStates.self, true, this.cachedStates.parent);
      this.cachedStates = undefined;
    }
  }
Validate the current state.  If setState(state) was called while this graph was not current,
all calculations were deferred. This makes sure that the current view is up to date with the
most current state.