focusInnerElement() {
      const isReversed = this._areValuesReversed();
      const affectedValue = this._valueAffected;
      if (this._isPressInCurrentRange || !affectedValue) {
        this._progressBar.focus();
      }
      if (affectedValue === "startValue" && !isReversed || affectedValue === "endValue" && isReversed) {
        this._startHandle.focus();
      }
      if (affectedValue === "endValue" && !isReversed || affectedValue === "startValue" && isReversed) {
        this._endHandle.focus();
      }
    }
Manage the focus between the focusable inner elements within the component.

On initial focusin or if the whole range is affected by the user interaction
set the focus on the progress selection, otherwise on one of the Range Slider
handles based on the determined affected value by the user action.

If one of the handles came across the other one in result of a user action
switch the focus between them to keep it visually consistent.

Note:
In some cases this function is going to get called twice on one user action.

1. When the focus is initially set to an inner element it is done in the very beginning,
of an interaction - on 'mousedown' and 'keydown' events. The focus of the host custom element
is still not being received, causining an immediate focusout that we prevent by
calling this function once again.

2. When the focused is manually switched from one inner element to another.
The focusout handler is one and the same for all focusable parts within the
Range Slider and when is called it checks if it should keep the focus within
the component and which part of it should get focused if that is the case.

@protected