Allow ConfirmDialog to confirm disabling options.

chrome/browser/resources/options/confirm_dialog.js

 // Copyright (c) 2012 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 */ var SettingsDialog = options.SettingsDialog;
 
   /**
    * A dialog that will pop up when the user attempts to set the value of the
    * Boolean |pref| to |true|, asking for confirmation. If the user clicks OK,
    * the new value is committed to Chrome. If the user clicks Cancel or leaves
    * the settings page, the new value is discarded.
    * @constructor
    * @param {string} name See Page constructor.
    * @param {string} title See Page constructor.
    * @param {string} pageDivName See Page constructor.
    * @param {HTMLButtonElement} okButton The confirmation button element.
    * @param {HTMLButtonElement} cancelButton The cancellation button element.
    * @param {string} pref The pref that requires confirmation.
    * @param {string} metric User metrics identifier.
    * @param {string=} opt_confirmedPref A pref used to remember whether the
    *     user has confirmed the dialog before. This ensures that the user is
    *     presented with the dialog only once. If left |undefined|, the dialog
    *     will pop up every time the user attempts to set |pref| to |true|.
+   * @param {boolean=} opt_confirmValue The value to which changing should
+   *     trigger the confirmation dialog.  Defaults to |true| if left
+   *     |undefined|.
    * @extends {options.SettingsDialog}
    */
   function ConfirmDialog(name, title, pageDivName, okButton, cancelButton, pref,
-                         metric, opt_confirmedPref) {
+                         metric, opt_confirmedPref, opt_confirmValue) {
     SettingsDialog.call(this, name, title, pageDivName, okButton, cancelButton);
 
     /** @protected */
     this.pref = pref;
 
     /** @protected */
     this.metric = metric;
 
     /** @private */
     this.confirmedPref_ = opt_confirmedPref;
 
     /** @private */
     this.confirmed_ = false;
+
+    /** @private */
+    this.confirmValue_ = opt_confirmValue == undefined ||

[dpapad, 2016/05/17 17:37:12]

"null == undefined" VS "null === undefined" behavior belongs in JS "bad parts"
IMO, since it is not intuitive at all. Other libraries address this by hiding
the complexity behind a utility isDef() method (like goog.isDef). 

My suggestion is to change it to the more intuitive and equivalent
this.confirmValue_ = opt_confirmValue === false ? false : true;

+        Boolean(opt_confirmValue);
   }
 
   ConfirmDialog.prototype = {
     // Set up the prototype chain
     __proto__: SettingsDialog.prototype,
 
     /**
      * Handle changes to |pref|. Only uncommitted changes are relevant as these
      * originate from user and need to be explicitly committed to take effect.
      * Pop up the dialog or commit the change, depending on whether confirmation
      * is needed.
      * @param {Event} event Change event.
      * @private
      */
     onPrefChanged_: function(event) {
       if (!event.value.uncommitted)
         return;
 
-      if (event.value.value && !this.confirmed_)
+      if (event.value.value == this.confirmValue_ && !this.confirmed_)
         PageManager.showPageByName(this.name, false);
       else
         Preferences.getInstance().commitPref(this.pref, this.metric);
     },
 
     /**
      * Handle changes to |confirmedPref_| by caching them.
      * @param {Event} event Change event.
      * @private
      */
@@ skipping 19 matching lines @@
      * Handle the confirm button by committing the |pref| change. If
      * |confirmedPref_| has been specified, also remember that the dialog has
      * been confirmed to avoid bringing it up in the future.
      * @override
      */
     handleConfirm: function() {
       SettingsDialog.prototype.handleConfirm.call(this);
 
       Preferences.getInstance().commitPref(this.pref, this.metric);
       if (this.confirmedPref_)
-        Preferences.setBooleanPref(this.confirmedPref_, true, true);
+        Preferences.setBooleanPref(
+            this.confirmedPref_, this.confirmValue_, true);
     },
 
     /**
      * Handle the cancel button by rolling back the |pref| change without it
      * ever taking effect.
      * @override
      */
     handleCancel: function() {
       SettingsDialog.prototype.handleCancel.call(this);
       Preferences.getInstance().rollbackPref(this.pref);
     },
 
     /**
      * When a user navigates away from a confirm dialog, treat as a cancel.
      * @protected
      * @override
      */
     willHidePage: function() {
       if (this.visible)
         Preferences.getInstance().rollbackPref(this.pref);
     },
   };
 
   return {
     ConfirmDialog: ConfirmDialog
   };
 });