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

chrome/browser/resources/offline_pages/offline_internals.js

Index: chrome/browser/resources/offline_pages/offline_internals.js
diff --git a/chrome/browser/resources/offline_pages/offline_internals.js b/chrome/browser/resources/offline_pages/offline_internals.js
index 7e4c2b197f45ed333f8117ce601de51ae07dd96d..baa0d181feaf049c62c42c543222fd0c0d8cd627 100644
--- a/chrome/browser/resources/offline_pages/offline_internals.js
+++ b/chrome/browser/resources/offline_pages/offline_internals.js
@@ -195,6 +195,15 @@ cr.define('offlineInternals', function() {
       $('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;
@@ -226,8 +235,8 @@ cr.define('offlineInternals', function() {
             });
       }
     };
-
-    refreshAll();
+    if (!incognito)
+      refreshAll();
   }
 
   // Return an object with all of the exports.