Using the Javascript-Voronoi (https://github.com/daviosa/Javascript-Voronoi) to draw voronoi edges on google maps. It draw lines to overlap your screen size. If the bounds of the map change, recalculate is needed.

voronoi-gmaps.js

var voronoi = new Voronoi();
var bbox = {xl:-window.innerWidth,xr:window.innerWidth*2,yt:-window.innerHeight,yb:window.innerHeight*2};
var voronoiLines = [];
var sites = [];

function resetVoronoi(){
  for(var vi in voronoiLines){
		var line = voronoiLines[vi];
		line.setMap(null);
	}
	voronoiLines = [];
	sites = [];
}

function calculateVoronoiGMaps(markersArray,map,overlay){
	resetVoronoi();
	for(var i in markersArray){
		var marker = markersArray[i];
		var p = fromLatLngToPoint(marker.getPosition(),overlay);
		sites.push({x:p.x, y:p.y});
	}
	var diagram = voronoi.compute(sites, bbox);
	for(var j in diagram.cells){
		var edges = [];
		var cell = diagram.cells[j];
		for(var hi in cell.halfedges){
			var edge = cell.halfedges[hi];
			var startPoint = fromPointToLatLng(new google.maps.Point(edge.getStartpoint().x,edge.getStartpoint().y),overlay);
			var endPoint = fromPointToLatLng(new google.maps.Point(edge.getEndpoint().x,edge.getEndpoint().y),overlay);
			var edgeLine = [startPoint,endPoint];
			var lineMap = new google.maps.Polyline({
			    path: edgeLine,
			    strokeColor: "#000000",
			    strokeOpacity: 1.0,
			    strokeWeight: 2
			  });
			lineMap.setMap(map);
			voronoiLines.push(lineMap);
		}
	}
}

function fromLatLngToPoint(latLng,overlay) {
  var p = overlay.getProjection().fromLatLngToContainerPixel(latLng);
	return p;
}

function fromPointToLatLng(point,overlay) {
	var coordinates = overlay.getProjection().fromContainerPixelToLatLng(point);
	return coordinates;
}