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

chrome/browser/resources/options/add_startup_page_overlay.js

 // Copyright (c) 2011 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() {
   const OptionsPage = options.OptionsPage;
   const ArrayDataModel = cr.ui.ArrayDataModel;
   const ListSingleSelectionModel = cr.ui.ListSingleSelectionModel;
 
   /**
@@ skipping 93 matching lines @@
 
     /**
       * Sets the value of the input field to the given string.
       * @private
       * @param {string} url String value to set the input field to.
       */
     setInputFieldValue_: function(url) {
       $('addStartupPageURL').value = url;
       this.updateAddButtonState_();
     },
+
+    /** @inheritDoc */
+    canShowPage: function() {
+      return !$('startupAddButton').disabled;

[stuartmorgan, 2011/02/12 01:09:06]

I'm not wild on using UI state for this. How about a "static" method on the
Browser page object that returns whether or not it should be enabled, and base
both this and the UI state updating on that method?

[Evan Stade, 2011/02/12 03:06:42]

There is already such a function, called
shouldEnableCustomStartupPageControls_(), and it also relies on "UI state". I
will use it here.

The scare quotes there indicate that I don't think this is UI state. I believe
this attribute is logically meaningful. The details of how it is represented in
the UI are abstracted (it happens to be greyed out, but that could be changed
with css right?). My point being, I believe that
shouldEnableCustomStartupPageControls_ is ok, even though it seems to contradict
the spirit of your comment.

+    },
   };
 
   AddStartupPageOverlay.updateRecentPageList = function(pages) {
     AddStartupPageOverlay.getInstance().updateRecentPageList_(pages);
   };
 
   AddStartupPageOverlay.setInputFieldValue = function(url) {
     AddStartupPageOverlay.getInstance().setInputFieldValue_(url);
   };
 
   // Export
   return {
     AddStartupPageOverlay: AddStartupPageOverlay
   };
 
 });