In the context of this exercise, if the call to
this.setState makes no changes to state, does it still call
this.setState will always lead to calling
shouldComponentUpdate returns false. By default,
shouldComponentUpdate always returns true.
To prevent this, you can override the implementation of
shouldComponentUpdate to return
false if there was no change in state, and
true only if there was a change in state. If it returns
render will not be called.