MD Settings: validate startup URLs

chrome/browser/resources/settings/on_startup_page/startup_urls_page.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.
 
 /**
  * @typedef {{
  *   'title': string,
  *   'tooltip': string,
  *   'url': string
  * }}
@@ skipping 24 matching lines @@
     prefs: {
       type: Object,
       notify: true,
     },
 
     /** @type {settings.StartupUrlsPageBrowserProxy} */
     browserProxy_: Object,
 
     /** @private {string} */
     newUrl_: {
+      observer: 'newUrlChanged_',
       type: String,
       value: '',
     },
 
+    isNewUrlValid_: {
+      type: Boolean,
+      value: false,
+    },
+
     /**
      * Pages to load upon browser startup.
      * @private {!Array<!StartupPageInfo>}
      */
     startupPages_: Array,
   },
 
   created: function() {
     this.browserProxy_ = settings.StartupUrlsPageBrowserProxyImpl.getInstance();
   },
@@ skipping 28 matching lines @@
   onUseCurrentPagesTap_: function() {
     this.browserProxy_.useCurrentPages();
   },
 
   /** @private */
   onCancelTap_: function() {
     this.$.addUrlDialog.close();
   },
 
   /**
-   * @return {boolean} Whether tapping the Add button should be allowed.
+   * @param {string} newUrl
    * @private
    */
-  isAddEnabled_: function() {
-    return this.browserProxy_.canAddPage(this.newUrl_);
+  newUrlChanged_: function(newUrl) {

[dschuyler, 2016/03/31 20:29:25]

There looks to be a small race condition here.
I think it can be avoided by setting isNewUrlValid_
to false here, before doing the validation.
The race I'm thinking of is having a valid URL
and then making it invalid and adding it before
the promise comes back.

[Dan Beam, 2016/03/31 22:06:55]

Done.

+    this.browserProxy_.validateStartupPage(newUrl).then(function(isValid) {
+      this.isNewUrlValid_ = isValid;
+    }.bind(this));
   },
 
   /** @private */
   onAddTap_: function() {
-    assert(this.isAddEnabled_());
+    assert(this.isNewUrlValid_);
     this.browserProxy_.addStartupPage(this.newUrl_);
     this.$.addUrlDialog.close();
   },
 
   /**
    * @param {!{model: !{index: number}}} e
    * @private
    */
   onRemoveUrlTap_: function(e) {
     this.browserProxy_.removeStartupPage(e.model.index);
   },
 });