MD Settings: Eliminate SettingsSubpageBrowsertest.

chrome/browser/resources/settings/settings_main/settings_main.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.
 
 /**
  * @typedef {{about: boolean, settings: boolean}}
  */
 var MainPageVisibility;
 
 /**
@@ skipping 56 matching lines @@
     toolbarSpinnerActive: {
       type: Boolean,
       value: false,
       notify: true,
     },
 
     /**
      * Dictionary defining page visibility.
      * @type {!GuestModePageVisibility}
      */
-    pageVisibility: {
-      type: Object,
-      value: function() {
-        return {};
-      },
-    },
+    pageVisibility: Object,
 
     showAndroidApps: Boolean,
   },
 
   /** @override */
   attached: function() {
     this.listen(this, 'freeze-scroll', 'onFreezeScroll_');
     this.listen(this, 'lazy-loaded', 'onLazyLoaded_');
   },
 
@@ skipping 190 matching lines @@
               text: this.showNoResultsFound_ ?
                   loadTimeData.getString('searchNoResults') :
                   loadTimeData.getStringF('searchResults', query)
             });
           }
         }.bind(this));
       }.bind(this), 0);
     }.bind(this));
   },
 });