[App Management] Follow up fixes to permission item.

This CL follows up crrev.com/c/1784238 with few naming and console
error fixes.

Bug: 999896
Change-Id: Ic053db94e250aebd38105ace7e895c468d3d30c7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1798255Reviewed-by: Alan Cutter <alancutter@chromium.org>
Commit-Queue: Jeevan Shikaram <jshikaram@chromium.org>
Cr-Commit-Position: refs/heads/master@{#699209}

chrome/browser/resources/settings/chromeos/os_apps_page/app_management_page/permission_item.html

@@ -24,7 +24,7 @@
      elements should import the icon-set needed for the specified |icon|. -->
     <template is="dom-if" if="[[available_]]">
       <app-management-toggle-row
-        id="toggleRow"
+        id="toggle-row"
         icon="[[icon]]"
         label="[[permissionLabel]]"
         managed="[[isManaged_(app_, permissionType)]]"

chrome/browser/resources/settings/chromeos/os_apps_page/app_management_page/permission_item.js

@@ -86,13 +86,14 @@ Polymer({
    * @return {boolean}
    */
   isManaged_: function(app, permissionType) {
-    if (app === undefined || permissionType === undefined) {
+    if (app === undefined || permissionType === undefined ||
+        !this.isAvailable_(app, permissionType)) {
       return false;
     }
 
     assert(app);
-
     const permission = app_management.util.getPermission(app, permissionType);
+
     assert(permission);
     return permission.isManaged;
   },
@@ -116,7 +117,7 @@ Polymer({
    * @private
    */
   onClick_: function() {
-    this.root.querySelector('#toggleRow').click();
+    this.$$('#toggle-row').click();
   },
 
   /**