MD Settings: add tests for <controlled-button>

chrome/browser/resources/settings/controls/controlled_button.js

Index: chrome/browser/resources/settings/controls/controlled_button.js
diff --git a/chrome/browser/resources/settings/controls/controlled_button.js b/chrome/browser/resources/settings/controls/controlled_button.js
index a072e37d91a1e3c5efce8b680a1533821033abb8..36392dbfdd8387e57b8e6cd785c11a0a1c47cac0 100644
--- a/chrome/browser/resources/settings/controls/controlled_button.js
+++ b/chrome/browser/resources/settings/controls/controlled_button.js
@@ -11,18 +11,17 @@ Polymer({
     /** @private */
     controlled_: {
       type: Boolean,
-      computed: 'computeControlled_(pref)',
+      computed: 'computeControlled_(pref.*)',
       reflectToAttribute: true,
     },
   },
 
   /**
-   * @param {!chrome.settingsPrivate.PrefObject} pref
    * @return {boolean} Whether the button is disabled.
    * @private
    */
-  computeControlled_: function(pref) {
-    return this.isPrefPolicyControlled(pref);
+  computeControlled_: function() {
+    return this.isPrefPolicyControlled(assert(this.pref));
   },
 
   /**