米尔侯赛因沙基尔的回答实际上是正确的。我一直在寻找一个答案，他给了它。他的格式和解释是可怕的，但。以下是我已经做到了（完全code）：

Mir Shakeel Hussain's answer is actually correct. I was looking for an answer and he gave it. His formatting and explanation is awful though. Here's how I've done it (complete code):

 var map;
 var poly; //the line
function initMap() {
  map = new google.maps.Map(document.getElementById('map'), {
    center: {lat: 52.092876, lng: 5.104480},
    zoom: 8
  });
}

$(document).ready(function () {
  $('#addLines').click(toggleLinesButton);
  $('#undoLine').click(undoPolyline);
});

var mayDrawLines = false;
function toggleLinesButton (el) {
  if (mayDrawLines) {
    mayDrawLines = false;
    $('#addLines').removeClass('active');
    removePoly();
  } else {
    mayDrawLines = true;
    $('#addLines').addClass('active');
    createPoly();
  }
}

var polyLineListener = null;
function createPoly () {
  if (!poly) {
    poly = new google.maps.Polyline({
      strokeColor: '#000000',
      strokeOpacity: 1.0,
      strokeWeight: 3
    });
    poly.setMap(map);
  }


  // Add a listener for the click event
  polyLineListener = google.maps.event.addListener(map, 'click', addLatLng);
}

function removePoly () {
  google.maps.event.removeListener(polyLineListener);
  //poly = null;
  polyLineListener = null;
}

var polyIndex = 0;
//Mirrors the path array to find index to delete and such
var mirrorCoordinates = [];
// Handles click events on a map, and adds a new point to the Polyline.
function addLatLng(event) {
  var path = poly.getPath();

  // Because path is an MVCArray, we can simply append a new coordinate
  // and it will automatically appear.
  path.push(event.latLng);
  mirrorCoordinates.push(event.latLng);

  polyIndex++;

  // Add a new marker at the new plotted point on the polyline.
  var marker = new google.maps.Marker({
    position: event.latLng,
    title: '#' + path.getLength(),
    map: map,
    visible: false
  });

}

function undoPolyline() {
  mirrorCoordinates.pop();
  polyIndex--;
  poly.getPath().setAt(polyIndex, mirrorCoordinates[mirrorCoordinates.length - 1]);
  poly.getPath().removeAt(polyIndex);
}