MD Settings: About page, setup for showing a sub-page.

chrome/browser/resources/settings/about_page/about_page.js

Index: chrome/browser/resources/settings/about_page/about_page.js
diff --git a/chrome/browser/resources/settings/about_page/about_page.js b/chrome/browser/resources/settings/about_page/about_page.js
index 5cced4f7244bbf44fbb09e31de0d38cd79dc7ff1..4c7fb9c36172c6ef566011dd579639538a70d43e 100644
--- a/chrome/browser/resources/settings/about_page/about_page.js
+++ b/chrome/browser/resources/settings/about_page/about_page.js
@@ -8,4 +8,35 @@
  */
 Polymer({
   is: 'settings-about-page',
+
+  behaviors: [RoutableBehavior],
+
+  properties: {
+    /**
+     * The current active route.
+     */
+    currentRoute: {
+      type: Object,
+      notify: true,
+    },
+  },
+
+  /**
+   * @type {string} Selector to get the sections.
+   * TODO(michaelpg): replace duplicate docs with @override once b/24294625
+   * is fixed.
+   */
+  sectionSelector: 'settings-section',
+
+   /** @override */
+  attached: function() {
+    this.scroller = this.parentElement;
+  },
+
+<if expr="chromeos">
+  /** @private */
+  onDetailedBuildInfoTap_: function() {
+    this.$.pages.setSubpageChain(['detailed-build-info']);
+  },
+</if>
 });