chromeos: Avoid NOTREACHED for MD settings power page.

chrome/browser/resources/settings/device_page/power.js

Index: chrome/browser/resources/settings/device_page/power.js
diff --git a/chrome/browser/resources/settings/device_page/power.js b/chrome/browser/resources/settings/device_page/power.js
index a04b51d6109e8879a03f4119c3a4eeeb015b1d10..817d1e97cdf23bc3f0697ac321a5ce1a7ac6385b 100644
--- a/chrome/browser/resources/settings/device_page/power.js
+++ b/chrome/browser/resources/settings/device_page/power.js
@@ -67,6 +67,11 @@ Polymer({
 
   /** @override */
   attached: function() {
+    // Even when the row is hidden, the element can still be attached via
+    // search.
+    if (!this.enablePowerSettings)
+      return;
+
     this.addWebUIListener(
         'battery-status-changed', this.set.bind(this, 'batteryStatus_'));
     this.addWebUIListener(