perf: Reduce Popper updates when placement don't change

[piecyk]

ScheduleUpdate is called twice per state change, as placement !== this.state.placement is not inside the setState callback, so the this.state is referring to current state and it's calling scheduleUpdate when the callback fires

In the same time in componentDidUpdate we have the

if (prevState.placement !== this.state.placement) {
  this.scheduleUpdate();
}

state placement changed, call the scheduleUpdate

Outcome of this is that on every new state.placement we call two time the scheduleUpdate IMHO it's redundant as scheduleUpdate is called at the same time.

[piecyk]

hmm, looks like this breaks correct position of popper at my internal tooltip implementation...
Need to look closer... will ping with results

[piecyk]

Checkout what was the problem... changing initial state placement value to what we pass in props is not good for poppers with arrow as we set placement to child function after we got first popper data.

After first placement, arrow is added with some margin that's increase popper element height and invalidates it's position.

Current flow,

1. first render, popper.js is triggered, state.placement = undefined
2. we got data, data.placement !== state.placement, trigger schedule update
3. we got data, data.placement === state.placement, done

initial placement on state should stay undefined

@FezVrasta it's ready

[FezVrasta]

thanks so much! merged