MD Settings: Debounce navigation event in side nav.

chrome/browser/resources/settings/settings_menu/settings_menu.js

 // Copyright 2015 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.
 
 /**
  * @fileoverview
  * 'settings-menu' shows a menu with a hardcoded set of pages and subpages.
  */
 Polymer({
   is: 'settings-menu',
@@ skipping 53 matching lines @@
    * @param {string} url
    */
   setSelectedUrl_: function(url) {
     this.$.topMenu.selected = this.$.subMenu.selected = url;
   },
 
   /**
    * @param {!Event} event
    * @private
    */
   onSelectorActivate_: function(event) {

[dschuyler, 2017/03/15 01:13:02]

I think we can remove the inner (nested) onSelectorActivate_ in the html file --
without adding the debounce. Does that work for you, WDYT?

[hcarmona, 2017/03/15 19:22:09]

This unfortunately doesn't work because the items in the advanced section aren't
direct children of the top iron-selector. :-\

The reason we get a double notification is because we set the other selector in
setSelectedUrl_, the HTML isn't double notifying

[hcarmona, 2017/03/16 00:58:19]

We spoke in person and I had misunderstood what you meant. Your proposed
solution works perfectly. This is because Polymer doesn't do filtering on the
target, so when an element listens it'll capture its children's events also.

I also said we might be able to get rid of some other properties: we need them
in order to highlight properly.

     this.setSelectedUrl_(event.detail.selected);
 
-    var path = new URL(event.detail.selected).pathname;
-    var route = settings.getRouteForPath(path);
-    assert(route, 'settings-menu has an entry with an invalid route.');
-    settings.navigateTo(
-        route, /* dynamicParams */ null, /* removeSearch */ true);
+    this.debounce('side-nav-route-change', function() {
+      var path = new URL(event.detail.selected).pathname;
+      var route = settings.getRouteForPath(path);
+      assert(route, 'settings-menu has an entry with an invalid route.');
+      settings.navigateTo(
+          route, /* dynamicParams */ null, /* removeSearch */ true);
+    });
   },
 
   /**
    * @param {boolean} opened Whether the menu is expanded.
    * @return {string} Which icon to use.
    * @private
    * */
   arrowState_: function(opened) {
     return opened ? 'cr:arrow-drop-up' : 'cr:arrow-drop-down';
   },
 });