MD Settings: Allow deleting read-only content setting exceptions.

chrome/browser/resources/settings/site_settings/site_list.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.
 
 /**
  * Enumeration mapping all possible controlled-by values for exceptions to
  * icons.
  * @enum {string}
  */
 var iconControlledBy = {
@@ skipping 44 matching lines @@
      * @private
      */
     showEditExceptionDialog_: Boolean,
 
     /**
      * Array of sites to display in the widget.
      * @type {!Array<SiteException>}
      */
     sites: {
       type: Array,
-      value: function() { return []; },
+      value: function() {
+        return [];
+      },
     },
 
     /**
      * Whether this list is for the All Sites category.
      */
     allSites: {
       type: Boolean,
       value: false,
     },
 
     /**
-      * The type of category this widget is displaying data for. Normally
-      * either 'allow' or 'block', representing which sites are allowed or
-      * blocked respectively.
-      */
+     * The type of category this widget is displaying data for. Normally
+     * either 'allow' or 'block', representing which sites are allowed or
+     * blocked respectively.
+     */
     categorySubtype: {
       type: String,
       value: settings.INVALID_CATEGORY_SUBTYPE,
     },
 
     /**
      * Whether to show the Allow action in the action menu.
      * @private
      */
     showAllowAction_: Boolean,
@@ skipping 30 matching lines @@
       type: Object,
       values: {
         ALLOW: 'Allow',
         BLOCK: 'Block',
         RESET: 'Reset',
         SESSION_ONLY: 'SessionOnly',
       }
     },
   },
 
-  observers: [
-    'configureWidget_(category, categorySubtype)'
-  ],
+  observers: ['configureWidget_(category, categorySubtype)'],
 
   ready: function() {
     this.addWebUIListener('contentSettingSitePermissionChanged',
         this.siteWithinCategoryChanged_.bind(this));
     this.addWebUIListener('onIncognitoStatusChanged',
         this.onIncognitoStatusChanged_.bind(this));
   },
 
   /**
    * Called when a site changes permission.
@@ skipping 63 matching lines @@
   hasSites_: function() {
     return !!this.sites.length;
   },
 
   /**
    * @param {string} source Where the setting came from.
    * @param {boolean} readOnlyList Whether the site exception list is read-only.
    * @return {boolean}
    * @private
    */
+  isResetButtonHidden_: function(source, readOnlyList) {
+    return this.isExceptionControlled_(source) || this.allSites ||
+        !readOnlyList;
+  },
+
+  /**
+   * @param {string} source Where the setting came from.
+   * @param {boolean} readOnlyList Whether the site exception list is read-only.
+   * @return {boolean}
+   * @private
+   */
   isActionMenuHidden_: function(source, readOnlyList) {
     return this.isExceptionControlled_(source) || this.allSites || readOnlyList;
   },
 
   /**
    * A handler for the Add Site button.
    * @param {!Event} e
    * @private
    */
   onAddSiteTap_: function(e) {
@@ skipping 260 matching lines @@
 
     if (item.incognito)
       return loadTimeData.getString('incognitoSite');
     return item.embeddingDisplayName;
   },
 
   /**
    * @param {!{model: !{item: !SiteException}}} e
    * @private
    */
+  onResetButtonTap_: function(e) {
+    // Trigger same logic as opening the menu and choosing the Reset item.
+    this.actionMenuSite_ = e.model.item;
+    this.onActionMenuActivate_(settings.PermissionValues.DEFAULT);
+    this.actionMenuSite_ = null;

[dschuyler, 2017/03/22 21:19:19]

Hmm, it looks like onActionMenuActivate_ is an event handler because the name
starts with "on", but it appears to only be used as a private function (and not
as an event handler -- maybe the name should be changed).

Your choice:

Could you do me the favor of adding a 
// TODO(dschuyler): Change onActionMenuActivate_() to take a actionMenuSite_ so
that it doesn't need to be set/reset like this.

or

Go ahead and change onActionMenuActivate_() to take a actionMenuSite_ so that it
doesn't need to be set/reset like this.

[tommycli, 2017/03/22 21:51:29]

Done. Based on your feedback, I refactored it a bit to make it more obvious.
Still room for more improvement, but this is a decent state I think.

+  },
+
+  /**
+   * @param {!{model: !{item: !SiteException}}} e
+   * @private
+   */
   onShowActionMenuTap_: function(e) {
     this.actionMenuSite_ = e.model.item;
     /** @type {!CrActionMenuElement} */ (
         this.$$('dialog[is=cr-action-menu]')).showAt(
             /** @type {!Element} */ (
                 Polymer.dom(/** @type {!Event} */ (e)).localTarget));
   },
 
   /** @private */
   closeActionMenu_: function() {
     this.actionMenuSite_ = null;
     var actionMenu = /** @type {!CrActionMenuElement} */ (
         this.$$('dialog[is=cr-action-menu]'));
     if (actionMenu.open)
       actionMenu.close();
   },
 });