[MD settings] close the side nav when navigating back/forward

This CL solves a problem with the side nav menu drawer staying open when
using the back/forward buttons. The drawer now closes when navigating
forward or back.

BUG=623903
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2170223002
Cr-Commit-Position: refs/heads/master@{#407290}

chrome/browser/resources/settings/settings_ui/settings_ui.js

@@ -66,6 +66,17 @@ Polymer({
     'sideNav.iron-activate': 'onIronActivate_',
   },
 
+  /** @override */
+  ready: function() {
+    this.$$('cr-toolbar').addEventListener('search-changed', function(e) {
+      this.$$('settings-main').searchContents(e.detail);
+    }.bind(this));
+
+    window.addEventListener('popstate', function(e) {
+      this.$$('app-drawer').close();
+    }.bind(this));
+  },
+
   /** @private */
   onCloseAppealTap_: function() {
     window.sessionStorage.appealClosed_ = this.appealClosed_ = true;
@@ -85,13 +96,6 @@ Polymer({
     this.$$('app-drawer').toggle();
   },
 
-  /** @override */
-  ready: function() {
-    this.$$('cr-toolbar').addEventListener('search-changed', function(e) {
-      this.$$('settings-main').searchContents(e.detail);
-    }.bind(this));
-  },
-
   /** @private */
   directionDelegateChanged_: function() {
     this.$$('app-drawer').align = this.directionDelegate.isRtl() ?