static updateGripCursors (angle) {
    const dirArr = Object.keys(selectorManager_.selectorGrips)
    let steps = Math.round(angle / 45)
    if (steps < 0) { steps += 8 }
    while (steps > 0) {
      dirArr.push(dirArr.shift())
      steps--
    }
    Object.values(selectorManager_.selectorGrips).forEach((gripElement, i) => {
      gripElement.setAttribute('style', ('cursor:' + dirArr[i] + '-resize'))
    })
  }
Updates cursors for corner grips on rotation so arrows point the right way.
@param {Float} angle - Current rotation angle in degrees
@returns {void}