Flesh out the location-page class to make it more general.

chrome/browser/resources/settings/site_settings/site_settings_behavior.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.
+
+/**
+ * @fileoverview Behavior common to Site Settings classes.
+ */
+
+/** @polymerBehavior */
+var SiteSettingsBehavior = {
+  /**
+   * Gets the pref at the given prefPath. Throws if the pref is not found.
+   * @param {string} prefPath
+   * @return {!chrome.settingsPrivate.PrefObject}
+   * @private
+   */
+  getPref_: function(prefPath) {

[michaelpg, 2015/10/22 16:11:34]

extract into separate behavior for this and settings-languages-singleton

[Finnur, 2015/10/26 14:38:05]

It is a bit unfortunate that behaviors can't inherit behaviors from other
behaviors, since this causes a bit of a cascading effect on isPrefEnabled...

[michaelpg, 2015/10/26 22:15:22]

You could override getPref_. Each behavior overrides any similarly named
behaviors before it in the behaviors list.

[Finnur, 2015/10/27 11:30:48]

I suspect you are suggestion a solution to a different problem than I'm having.
My problem is that I wanted to use getPref_ from within SiteSettingsBehavior,
and your suggestion provided a hint that made it possible (by defining the
PrefsBehavior *ahead* of the SiteSettingsBehavior). So, after all my problem
wasn't that I needed inheritance, although that would also have been a solution.

+    var pref = /** @type {!chrome.settingsPrivate.PrefObject} */(
+        this.get(prefPath, this.prefs));
+    assert(typeof pref != 'undefined', 'Pref is missing: ' + prefPath);
+    return pref;
+  },
+
+  /**
+   * Sets the value of the pref at the given prefPath. Throws if the pref is not
+   * found.
+   * @param {string} prefPath
+   * @param {*} value
+   * @private
+   */
+  setPrefValue_: function(prefPath, value) {

[michaelpg, 2015/10/22 16:11:34]

same

[Finnur, 2015/10/26 14:38:05]

Done.

+    this.set('prefs.' + prefPath + '.value', value);

[michaelpg, 2015/10/22 16:11:34]

contradictory to the comment, this doesn't throw if the pref is not found

[Finnur, 2015/10/26 14:38:05]

Done.

+  },
+
+  /**
+   * Returns whether the category default is set to enabled or not.
+   * @param {number} category The category to check.
+   * @return {boolean} True if the category default is set to enabled.
+   * @private
+   */
+  isPrefEnabled_: function(category) {
+    var pref = this.getPref_(this.computeTogglePrefName_(this.category));
+
+    // FullScreen is Allow vs. Ask.
+    if (category == settings.ContentSettingsTypes.FULLSCREEN)
+      return pref.value != settings.DefaultValues.ALLOW;
+
+    return pref.value != settings.DefaultValues.BLOCK;
+  },
+
+  /**
+   * A utility function to compute the icon to use for the category.
+   * @param {number} category The category to show the icon for.
+   * @return {string} The id of the icon for the given category.
+   * @private
+   */
+  computeIcon_: function(category) {
+    // Wonder if any of these enum values are directly accessible from .js?

[michaelpg, 2015/10/22 16:11:34]

make a TODO or remove comment (i'm not sure what this comment means)

[Finnur, 2015/10/26 14:38:05]

Removed (the todo is kind of covered already in constants.js).

+    switch (category) {
+      case settings.ContentSettingsTypes.COOKIES:
+        return '';  // Haven't found a good cookies icon under iron-icons.
+      case settings.ContentSettingsTypes.JAVASCRIPT:
+        return 'icons:input';
+      case settings.ContentSettingsTypes.FULLSCREEN:
+        return 'icons:fullscreen';
+      case settings.ContentSettingsTypes.POPUPS:
+        return 'icons:open-in-new';
+      case settings.ContentSettingsTypes.GEOLOCATION:
+        return 'communication:location-on';
+      case settings.ContentSettingsTypes.NOTIFICATION:
+        return 'social:notifications';
+      case settings.ContentSettingsTypes.CAMERA:
+        return 'av:videocam';
+      case settings.ContentSettingsTypes.MIC:
+        return 'av:mic';
+      default:
+        assertNotReached();
+        return '';
+    }
+  },
+
+  /**
+   * A utility function to compute the title of the category.
+   * @param {number} category The category to show the title for.
+   * @return {string} The title for the given category.
+   * @private
+   */
+  computeTitle_: function(category) {
+    switch (category) {
+      case settings.ContentSettingsTypes.COOKIES:
+        return loadTimeData.getString('siteSettingsCookies');
+      case settings.ContentSettingsTypes.JAVASCRIPT:
+        return loadTimeData.getString('siteSettingsJavascript');
+      case settings.ContentSettingsTypes.FULLSCREEN:
+        return loadTimeData.getString('siteSettingsFullscreen');
+      case settings.ContentSettingsTypes.POPUPS:
+        return loadTimeData.getString('siteSettingsPopups');
+      case settings.ContentSettingsTypes.GEOLOCATION:
+        return loadTimeData.getString('siteSettingsLocation');
+      case settings.ContentSettingsTypes.NOTIFICATION:
+        return loadTimeData.getString('siteSettingsNotifications');
+      case settings.ContentSettingsTypes.CAMERA:
+        return loadTimeData.getString('siteSettingsCamera');
+      case settings.ContentSettingsTypes.MIC:
+        return loadTimeData.getString('siteSettingsMic');
+      default:
+        assertNotReached();
+        return '';
+    }
+  },
+
+  /**
+   * A utility function to compute the name of the pref for the category.
+   * @param {number} category The category to find the pref name for.
+   * @return {string} The pref name for the given category.
+   * @private
+   */
+  computeTogglePrefName_: function(category) {
+    return 'profile.default_content_setting_values.' +
+        this.computeCategorySuffix_(category);
+  },
+
+  /**
+   * A utility function to compute the name of the pref for the exceptions
+   * for a given category.
+   * @param {number} category The category to find the pref name for.
+   * @return {string} The pref name for the given category exceptions.
+   * @private
+   */
+  computeExceptionsPrefName_: function(category) {
+    return 'profile.content_settings.exceptions.' +
+        this.computeCategorySuffix_(category);
+  },
+
+  /**
+   * A utility function to convert the category enum into its text
+   * representation, for use with prefs.
+   * @param {number} category The category to find the pref name for.
+   * @return {string} The pref name (suffix) for the given category.
+   * @private
+   */
+  computeCategorySuffix_: function(category) {
+    switch (category) {
+      case settings.ContentSettingsTypes.COOKIES:
+        return 'cookies';
+      case settings.ContentSettingsTypes.JAVASCRIPT:
+        return 'javascript';
+      case settings.ContentSettingsTypes.FULLSCREEN:
+        return 'fullscreen';
+      case settings.ContentSettingsTypes.POPUPS:
+        return 'popups';
+      case settings.ContentSettingsTypes.GEOLOCATION:
+        return 'geolocation';
+      case settings.ContentSettingsTypes.NOTIFICATION:
+        return 'notifications';
+      case settings.ContentSettingsTypes.CAMERA:
+        return 'media_stream_camera';
+      case settings.ContentSettingsTypes.MIC:
+        return 'media_stream_mic';
+      default:
+        assertNotReached();
+        return '';
+    }
+  },
+
+  /**
+   * A utility function to compute the description for the category.
+   * @param {number} category The category to show the description for.
+   * @param {boolean} categoryEnabled The state of the global toggle.
+   * @return {string} The category description.
+   * @private
+   */
+  computeDesc_: function(category, categoryEnabled) {
+    switch (category) {
+      case settings.ContentSettingsTypes.JAVASCRIPT:
+        // "Allowed (recommended)" vs "Blocked".
+        return categoryEnabled ?
+            loadTimeData.getString('siteSettingsAllowedRecommended') :
+            loadTimeData.getString('siteSettingsBlocked');
+      case settings.ContentSettingsTypes.POPUPS:
+        // "Allowed" vs "Blocked (recommended)".
+        return categoryEnabled ?
+            loadTimeData.getString('siteSettingsAllowed') :
+            loadTimeData.getString('siteSettingsBlockedRecommended');
+      case settings.ContentSettingsTypes.NOTIFICATION:
+        // "Ask before sending (recommended)" vs "Blocked".
+        return categoryEnabled ?
+            loadTimeData.getString('siteSettingsAskBeforeSending') :
+            loadTimeData.getString('siteSettingsBlocked');
+      case settings.ContentSettingsTypes.GEOLOCATION:
+      case settings.ContentSettingsTypes.CAMERA:
+      case settings.ContentSettingsTypes.MIC:
+        // "Ask before accessing (recommended)" vs "Blocked".
+        return categoryEnabled ?
+            loadTimeData.getString('siteSettingsAskBeforeAccessing') :
+            loadTimeData.getString('siteSettingsBlocked');
+      case settings.ContentSettingsTypes.FULLSCREEN:
+        // "Allowed" vs. "Ask first (recommended)".
+        return categoryEnabled ?
+            loadTimeData.getString('siteSettingsAllowed') :
+            loadTimeData.getString('siteSettingsAskFirstRecommended');
+      case settings.ContentSettingsTypes.COOKIES:
+        // "Allow sites to save and read cookie data" vs "Blocked".
+        return categoryEnabled ?
+            loadTimeData.getString('siteSettingsCookiesAllowed') :
+            loadTimeData.getString('siteSettingsBlocked');
+      default:
+        assertNotReached();
+        return '';
+    }
+  },
+};