MD Settings: validate startup URLs

chrome/browser/resources/settings/on_startup_page/startup_urls_page.js

Index: chrome/browser/resources/settings/on_startup_page/startup_urls_page.js
diff --git a/chrome/browser/resources/settings/on_startup_page/startup_urls_page.js b/chrome/browser/resources/settings/on_startup_page/startup_urls_page.js
index c8ba1c61264f02f3122c94ac2c8d9cff95daed12..a4543a6e27dcf58ca4ed969d1bef78302415fb16 100644
--- a/chrome/browser/resources/settings/on_startup_page/startup_urls_page.js
+++ b/chrome/browser/resources/settings/on_startup_page/startup_urls_page.js
@@ -42,10 +42,16 @@ Polymer({
 
     /** @private {string} */
     newUrl_: {
+      observer: 'newUrlChanged_',
       type: String,
       value: '',
     },
 
+    isNewUrlValid_: {

[dpapad, 2016/03/31 18:39:56]

Nit(optional): When the default value is false you can shorten more

isNewUrlValid_ : Boolean,

[Dan Beam, 2016/03/31 22:06:54]

i wouldn't encourage this, as one might assume the default is false, but it's
not crystal clear from looking at this site

+      type: Boolean,
+      value: false,
+    },
+
     /**
      * Pages to load upon browser startup.
      * @private {!Array<!StartupPageInfo>}
@@ -93,17 +99,16 @@ Polymer({
     this.$.addUrlDialog.close();
   },
 
-  /**
-   * @return {boolean} Whether tapping the Add button should be allowed.
-   * @private
-   */
-  isAddEnabled_: function() {
-    return this.browserProxy_.canAddPage(this.newUrl_);
+  /** @private */
+  newUrlChanged_: function() {
+    this.browserProxy_.validateStartupPage(this.newUrl_).then(function(valid) {
+      this.isNewUrlValid_ = valid;

[dpapad, 2016/03/31 18:39:56]

Nit (optional): s/valid/isValid

[Dan Beam, 2016/03/31 22:06:54]

Done.

+    }.bind(this));
   },
 
   /** @private */
   onAddTap_: function() {
-    assert(this.isAddEnabled_());
+    assert(this.isNewUrlValid_);
     this.browserProxy_.addStartupPage(this.newUrl_);
     this.$.addUrlDialog.close();
   },