[Offline pages] Add null pointer checks in offline internals code

chrome/browser/resources/offline_pages/offline_internals.js

 // Copyright 2016 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.
 
 cr.define('offlineInternals', function() {
   'use strict';
 
   /** @type {!Array<OfflinePage>} */
   var offlinePages = [];
 
@@ skipping 177 matching lines @@
     }
 
     /**
      * @param {!boolean} enabled Whether to enable Logging.
      */
     function toggleRequestQueueLog(enabled) {
       browserProxy_.setRecordRequestQueue(enabled);
       $('request-status').textContent = enabled ? 'On' : 'Off';
     }
 
+    var incognito = loadTimeData.getBoolean('isIncognito');
+    $('clear-all').disabled = incognito;
+    $('clear-selected').disabled = incognito;
+    $('log-model-on').disabled = incognito;
+    $('log-model-off').disabled = incognito;
+    $('log-request-on').disabled = incognito;
+    $('log-request-off').disabled = incognito;
+    $('refresh').disabled = incognito;
+
     $('clear-all').onclick = deleteAllPages;
     $('clear-selected').onclick = deleteSelectedPages;
     $('refresh').onclick = refreshAll;
     $('download').onclick = download;
     $('log-model-on').onclick = togglePageModelLog.bind(this, true);
     $('log-model-off').onclick = togglePageModelLog.bind(this, false);
     $('log-request-on').onclick = toggleRequestQueueLog.bind(this, true);
     $('log-request-off').onclick = toggleRequestQueueLog.bind(this, false);
     $('refresh-logs').onclick = refreshLog;
     $('add-to-queue').onclick = function() {
@@ skipping 11 matching lines @@
                 if (counter == 0) {
                   browserProxy_.getRequestQueue().then(fillRequestQueue);
                 }
               } else {
                 $('save-url-state').textContent +=
                     saveUrls[i] + ' failed to be added to queue.\n';
               }
             });
       }
     };
-
-    refreshAll();
+    if (!incognito)
+      refreshAll();
   }
 
   // Return an object with all of the exports.
   return {
     initialize: initialize,
   };
 });
 
 document.addEventListener('DOMContentLoaded', offlineInternals.initialize);