Rolling forward https://codereview.chromium.org/1155683008/ which was

third_party/polymer/v1_0/components-chromium/more-routing/driver/path-extracted.js

 
 (function(scope) {
 var MoreRouting = scope.MoreRouting = scope.MoreRouting || {};
 MoreRouting.PathDriver = PathDriver;
 
 /**
  * TODO(nevir): Docs.
  */
 function PathDriver() {
   MoreRouting.Driver.apply(this, arguments);
   this._bindEvents();
   this._read();
 }
 PathDriver.prototype = Object.create(MoreRouting.Driver.prototype);
 
 PathDriver.prototype.navigateToUrl = function navigateToUrl(url) {
   window.history.pushState({}, '', url);
   this._read();
 };
 
 PathDriver.prototype._bindEvents = function _bindEvents() {
   window.addEventListener('popstate', this._read.bind(this));
 };
 
 PathDriver.prototype._read = function _read() {
   this.setCurrentPath(window.location.pathname);
 };
 
 })(window);