Settings Router Refactor: Normalize URL only for main settings page.

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 245 matching lines @@
   var getRouteForPath = function(path) {
     // TODO(tommycli): Use Object.values once Closure compilation supports it.
     var matchingKey = Object.keys(Route).find(function(key) {
       return Route[key].path == path;
     });
 
     return Route[matchingKey] || null;
   };
 
   /**
-   * The current active route. This updated only by settings.navigateTo.
+   * The current active route. This updated is only by settings.navigateTo or
+   * settings.initializeRouteFromUrl.
    * @private {!settings.Route}
    */
   var currentRoute_ = Route.BASIC;
 
   /**
-   * The current query parameters. This updated only by settings.navigateTo.
+   * The current query parameters. This is updated only by settings.navigateTo
+   * or settings.initializeRouteFromUrl.
    * @private {!URLSearchParams}
    */
   var currentQueryParameters_ = new URLSearchParams();
 
-  // Initialize the route and query params from the URL.
-  (function() {
+  /** @private */
+  var initializeRouteFromUrlCalled_ = false;
+
+  /**
+   * Initialize the route and query params from the URL.
+   */
+  var initializeRouteFromUrl = function() {
+    assert(!initializeRouteFromUrlCalled_);
+    initializeRouteFromUrlCalled_ = true;
+
     var route = getRouteForPath(window.location.pathname);
     if (route) {
       currentRoute_ = route;
       currentQueryParameters_ = new URLSearchParams(window.location.search);
     } else {
-      window.history.pushState(undefined, '', Route.BASIC.path);
+      window.history.replaceState(undefined, '', Route.BASIC.path);
     }
-  })();
+  };
 
   /**
    * Helper function to set the current route and notify all observers.
    * @param {!settings.Route} route
    * @param {!URLSearchParams} queryParameters
    */
   var setCurrentRoute = function(route, queryParameters) {
     var oldRoute = currentRoute_;
     currentRoute_ = route;
     currentQueryParameters_ = queryParameters;
@@ skipping 39 matching lines @@
   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,
                     new URLSearchParams(window.location.search));
   });
 
   return {
     Route: Route,
     RouteObserverBehavior: RouteObserverBehavior,
     getRouteForPath: getRouteForPath,
+    initializeRouteFromUrl: initializeRouteFromUrl,
     getCurrentRoute: getCurrentRoute,
     getQueryParameters: getQueryParameters,
     navigateTo: navigateTo,
   };
 });