MD Settings: Preserve search URL param in subpages.

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 300 matching lines @@
 
   /** @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.
+   *     URL parameters in a different order will still push to history.
+   * @param {boolean=} opt_removeSearch Whether to strip the 'search' URL
+   *     parameter during navigation. Defaults to false.
    */
-  var navigateTo = function(route, opt_dynamicParameters) {
+  var navigateTo = function(route, opt_dynamicParameters, opt_removeSearch) {

[dpapad, 2016/11/09 23:34:22]

Per our discussion, I reversed preserveSearch to removeSearch, such that the
default value can be false, which makes it more readable.

     var params = opt_dynamicParameters || new URLSearchParams();
+    var removeSearch = !!opt_removeSearch;
+
+    var oldSearchParam = getQueryParameters().get('search') || '';
+    var newSearchParam = params.get('search') || '';
+
+    if (!removeSearch && oldSearchParam && !newSearchParam)
+      params.append('search', oldSearchParam);
 
     var url = route.path;
-    if (opt_dynamicParameters) {
-      var queryString = opt_dynamicParameters.toString();
-      if (queryString)
-        url += '?' + queryString;
-    }
+    var queryString = params.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, 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.
@@ skipping 20 matching lines @@
     RouteObserverBehavior: RouteObserverBehavior,
     getRouteForPath: getRouteForPath,
     initializeRouteFromUrl: initializeRouteFromUrl,
     getCurrentRoute: getCurrentRoute,
     getQueryParameters: getQueryParameters,
     lastRouteChangeWasPopstate: lastRouteChangeWasPopstate,
     navigateTo: navigateTo,
     navigateToPreviousRoute: navigateToPreviousRoute,
   };
 });