Settings Router Refactor: Improve chrome://md-settings/foobar behavior.

chrome/browser/resources/settings/route.js

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 cr.define('settings', function() {
   /**
    * Class for navigable routes. May only be instantiated within this file.
    * @constructor
    * @param {string} path
    * @private
@@ skipping 278 matching lines @@
     });
 
     return Route[matchingKey] || null;
   };
 
   /**
    * The current active route. This may only be updated via the global
    * function settings.navigateTo.
    * @private {!settings.Route}
    */
-  var currentRoute_ = getRouteForPath(window.location.pathname) || Route.BASIC;
+  var currentRoute_ = (function() {
+    var route = getRouteForPath(window.location.pathname);
+    if (route)
+      return route;
+
+    // Reset the URL path to '/' if the user navigates to a nonexistent URL.
+    window.history.replaceState(undefined, '', Route.BASIC.path);
+    return Route.BASIC;
+  })();

[Dan Beam, 2016/08/02 00:11:04]

how would this leak global variables?

var currentRoute_ = getRouteForPath(window.location.pathname);
if (!currentRoute_) {
  currentRoute_ = Route.BASIC;
  window.history.replaceState(undefined, '', Route.BASIC.path);
}

does closure complain because this yields ?settings.Route for 1 statement?

[tommycli, 2016/08/02 00:14:29]

Yeah, it complains :D

 
   /**
    * Helper function to set the current route and notify all observers.
    * @param {!settings.Route} route
    */
   var setCurrentRoute = function(route) {
     currentRoute_ = route;
     for (var observer of routeObservers_)
       observer.currentRouteChanged();
   };
 
   /** @return {!settings.Route} */
   var getCurrentRoute = function() { return currentRoute_; };
 
   /**
    * Navigates to a canonical route and pushes a new history entry.
    * @param {!settings.Route} route
    * @private
    */
   var navigateTo = function(route) {
     if (assert(route) == currentRoute_)
       return;
 
-    window.history.pushState(undefined, document.title, route.path);
+    window.history.pushState(undefined, '', route.path);
     setCurrentRoute(route);
   };
 
   window.addEventListener('popstate', function(event) {
     // On pop state, do not push the state onto the window.history again.
     setCurrentRoute(getRouteForPath(window.location.pathname) || Route.BASIC);
   });
 
   return {
     Route: Route,
     RouteObserverBehavior: RouteObserverBehavior,
     getRouteForPath: getRouteForPath,
     getCurrentRoute: getCurrentRoute,
     navigateTo: navigateTo,
   };
 });