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

chrome/browser/resources/settings/prefs/prefs_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 Common prefs behavior.
+ */
+
+/** @polymerBehavior */
+var PrefsBehavior = {
+  /**
+   * Gets the pref at the given prefPath. Throws if the pref is not found.
+   * @param {string} prefPath
+   * @return {!chrome.settingsPrivate.PrefObject}
+   * @protected
+   */
+  getPref: function(prefPath) {
+    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
+   * @protected
+   */
+  setPrefValue: function(prefPath, value) {
+    this.getPref(prefPath);  // Ensures we throw if the pref is not found.
+    this.set('prefs.' + prefPath + '.value', value);
+  },
+};