Use dom-if to hide settings pages and show explicitly.

chrome/browser/resources/settings/settings_page/settings_page_visibility.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 controlling the visibility of Settings pages.
+ *
+ * Example:
+ *   behaviors: [SettingsPageVisibility],
+ *
+ * @group Chrome UI Behavior
+ */
+
+/**
+ * Set this to true in tests before loading the page (e.g. in preLoad()) so that
+ * pages do not initially get created. Set this to false BEFORE modifying
+ * pageVisibility. NOTE: Changing this value after the DOM is loaded will not
+ * trigger a visibility change, pageVisibility must be modified to trigger data
+ * binding events.
+ * @type {boolean}
+ */
+var SettingsHideAllPagesForTest;

[Dan Beam, 2015/12/08 02:55:27]

nit: settingsHideAllPagesForTest

[stevenjb, 2015/12/08 20:07:37]

Done.

+
+/** @polymerBehavior */
+var SettingsPageVisibility = {
+  properties: {
+    /**
+     * Dictionary defining page visibility. If not set for a page, visibility
+     * will default to true (unless SettingsHideAllPagesForTest is set).
+     * @type {Object<string, boolean>}

[michaelpg, 2015/12/08 00:45:58]

nit: just Object<boolean>, keys are always strings

[Dan Beam, 2015/12/08 02:55:27]

+1 (I thought we had a presubmit about this?)

[stevenjb, 2015/12/08 20:07:37]

Done. (And apparently not, we have 128 instances of Object<string, ...> in the
Chrome source FWIW).

+     */
+    pageVisibility: {
+      type: Object,
+      value: function() { return {}; },
+      notify: true,

[michaelpg, 2015/12/08 00:45:58]

notify: true is unnecessary -- no one is two-way binding to this, right?

[stevenjb, 2015/12/08 20:07:37]

Not currently... and probably not ever. Done.

+    },
+  },
+
+  /**
+   * @param {boolean} visibility
+   * @return {boolean}
+   */
+  showPage: function(visibility) {
+    return !SettingsHideAllPagesForTest && visibility !== false;
+  },
+};