chrome://settings - Provide method for pages to prevent themselves being shown.

chrome/browser/resources/options/alert_overlay.js

 // Copyright (c) 2010 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('options', function() {
   var OptionsPage = options.OptionsPage;
 
   /**
    * AlertOverlay class
    * Encapsulated handling of a generic alert.
    * @class
    */
   function AlertOverlay() {
     OptionsPage.call(this, 'alertOverlay', '', 'alertOverlay');
   }
 
   cr.addSingletonGetter(AlertOverlay);
 
   AlertOverlay.prototype = {
     // Inherit AlertOverlay from OptionsPage.
     __proto__: OptionsPage.prototype,
 
     /**
+     * Whether the page can be shown. Used to make sure the page is only
+     * shown via AlertOverlay.Show(), and not via the address bar.
+     * @private
+     */
+    canShow_: false,
+
+    /**
      * Initialize the page.
      */
     initializePage: function() {
       // Call base class implementation to start preference initialization.
       OptionsPage.prototype.initializePage.call(this);
 
       var self = this;
       $('alertOverlayOk').onclick = function(event) {
         self.handleOK_();
       };
@@ skipping 18 matching lines @@
     /**
      * Handle the 'cancel' button.  Clear the overlay and call the cancel
      * callback if available.
      * @private
      */
     handleCancel_: function() {
       OptionsPage.closeOverlay();
       if (this.cancelCallback != undefined) {
         this.cancelCallback.call();
       }
-    }
+    },
+
+    /**
+     * The page is getting hidden. Don't let it be shown again.
+     */
+    willHidePage: function() {
+      canShow_ = false;

[Vitaly Pavlenko, 2014/10/01 23:29:53]

This should be 

this.canShow_ = false;

right?

[Evan Stade, 2014/10/13 16:21:55]

yes

+    },
+
+    /** @inheritDoc */
+    canShowPage: function() {
+      return this.canShow_;
+    },
   };
 
   /**
    * Show an alert overlay with the given message, button titles, and
    * callbacks.
    * @param {string} title The alert title to display to the user.
    * @param {string} message The alert message to display to the user.
    * @param {string} okTitle The title of the OK button. If undefined or empty,
    *     no button is shown.
    * @param {string} cancelTitle The title of the cancel button. If undefined or
@@ skipping 28 matching lines @@
       $('alertOverlayOk').style.display = 'none';
     }
 
     if (cancelTitle != undefined && cancelTitle != '') {
       $('alertOverlayCancel').textContent = cancelTitle;
       $('alertOverlayCancel').style.display = 'inline';
     } else {
       $('alertOverlayCancel').style.display = 'none';
     }
 
-    AlertOverlay.getInstance().okCallback = okCallback;
-    AlertOverlay.getInstance().cancelCallback = cancelCallback;
+    var alertOverlay = AlertOverlay.getInstance();
+    alertOverlay.okCallback = okCallback;
+    alertOverlay.cancelCallback = cancelCallback;
+    alertOverlay.canShow_ = true;
 
+    // Intentionally don't show the URL in the location bar as we don't want
+    // people trying to navigate here by hand.
     OptionsPage.showPageByName('alertOverlay', false);
   }
 
   // Export
   return {
     AlertOverlay: AlertOverlay
   };
 });