MD Settings: Prevent unexpected scrolling to section on popstates.

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 235 matching lines @@
    */
   var currentRoute_ = Route.BASIC;
 
   /**
    * The current query parameters. This is updated only by settings.navigateTo
    * or settings.initializeRouteFromUrl.
    * @private {!URLSearchParams}
    */
   var currentQueryParameters_ = new URLSearchParams();
 
+  /** @private {boolean} */
+  var lastRouteChangeWasPopstate_ = false;
+
   /** @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);
     // Never allow direct navigation to ADVANCED.
     if (route && route != Route.ADVANCED) {
       currentRoute_ = route;
       currentQueryParameters_ = new URLSearchParams(window.location.search);
     } else {
       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
+   * @param {boolean} isPopstate
    */
-  var setCurrentRoute = function(route, queryParameters) {
+  var setCurrentRoute = function(route, queryParameters, isPopstate) {
     var oldRoute = currentRoute_;
     currentRoute_ = route;
     currentQueryParameters_ = queryParameters;
+    lastRouteChangeWasPopstate_ = isPopstate;
     for (var observer of routeObservers_)
       observer.currentRouteChanged(currentRoute_, oldRoute);
   };
 
   /** @return {!settings.Route} */
   var getCurrentRoute = function() { return currentRoute_; };
 
   /** @return {!URLSearchParams} */
   var getQueryParameters = function() {
     return new URLSearchParams(currentQueryParameters_);  // Defensive copy.
   };
 
+  /** @return {boolean} */
+  var lastRouteChangeWasPopstate = function() {
+    return lastRouteChangeWasPopstate_;
+  };
+
   /**
    * Navigates to a canonical route and pushes a new history entry.
    * @param {!settings.Route} route
    * @param {URLSearchParams=} opt_dynamicParameters Navigations to the same
    *     search parameters in a different order will still push to history.
    */
   var navigateTo = function(route, opt_dynamicParameters) {
     var params = opt_dynamicParameters || new URLSearchParams();
 
     var url = route.path;
     if (opt_dynamicParameters) {
       var queryString = opt_dynamicParameters.toString();
       if (queryString)
         url += '?' + queryString;
     }
 
     // History serializes the state, so we don't push the actual route object.
     window.history.pushState(currentRoute_.path, '', url);
-    setCurrentRoute(route, params);
+    setCurrentRoute(route, params, false);
   };
 
   /**
    * Navigates to the previous route if it has an equal or lesser depth.
    * If there is no previous route in history meeting those requirements,
    * this navigates to the immediate parent. This will never exit Settings.
    */
   var navigateToPreviousRoute = function() {
     var previousRoute =
         window.history.state &&
         assert(getRouteForPath(/** @type {string} */ (window.history.state)));
 
     if (previousRoute && previousRoute.depth <= currentRoute_.depth)
       window.history.back();
     else
       navigateTo(currentRoute_.parent || Route.BASIC);
   };
 
   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));
+                    new URLSearchParams(window.location.search), true);
   });
 
   return {
     Route: Route,
     RouteObserverBehavior: RouteObserverBehavior,
     getRouteForPath: getRouteForPath,
     initializeRouteFromUrl: initializeRouteFromUrl,
     getCurrentRoute: getCurrentRoute,
     getQueryParameters: getQueryParameters,
+    lastRouteChangeWasPopstate: lastRouteChangeWasPopstate,
     navigateTo: navigateTo,
     navigateToPreviousRoute: navigateToPreviousRoute,
   };
 });