Fix thumbnails in the guest mode.

chrome/browser/resources/image_loader/request.js

 // Copyright 2013 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.
 
 'use strict';
 
 /**
  * Creates and starts downloading and then resizing of the image. Finally,
  * returns the image using the callback.
  *
@@ skipping 242 matching lines @@
   // Fetches the access token and makes an authorized call. If refresh is true,
   // then forces refreshing the access token.
   var requestTokenAndCall = function(refresh, onInnerSuccess, onInnerFailure) {
     chrome.fileBrowserPrivate.requestAccessToken(refresh, function(token) {
       if (this.aborted_)
         return;
       if (!token) {
         onInnerFailure();
         return;
       }
-      this.xhr_ = AuthorizedXHR.loadWithToken_(
+      this.xhr_ = AuthorizedXHR.load_(
           token, url, onInnerSuccess, onInnerFailure);
     }.bind(this));
   }.bind(this);
 
   // Refreshes the access token and retries the request.
   var maybeRetryCall = function(code) {
     if (this.aborted_)
       return;
     requestTokenAndCall(true, onMaybeSuccess, onMaybeFailure);
   }.bind(this);
 
+  // Do not request a token for local resources, since it is not necessary.
+  if (url.indexOf('filesystem:') === 0) {
+    this.xhr_ = AuthorizedXHR.load_(null, url, onMaybeSuccess, onMaybeFailure);
+    return;
+  }
+
   // Make the request with reusing the current token. If it fails, then retry.
   requestTokenAndCall(false, onMaybeSuccess, maybeRetryCall);
 };
 
 /**
  * Fetches data using authorized XmlHttpRequest with the provided OAuth2 token.
  * If the token is invalid, the request will fail.
  *
- * @param {string} token OAuth2 token to be injected to the request.
+ * @param {?string} token OAuth2 token to be injected to the request. Null for
+ *     no token.
  * @param {string} url URL to the resource to be fetched.
  * @param {function(string, Blob}) onSuccess Success callback with the content
  *     type and the fetched data.
  * @param {function(number=)} onFailure Failure callback with the error code
  *     if available.
+ * @return {AuthorizedXHR} XHR instance.
  * @private
  */
-AuthorizedXHR.loadWithToken_ = function(token, url, onSuccess, onFailure) {
+AuthorizedXHR.load_ = function(token, url, onSuccess, onFailure) {
   var xhr = new XMLHttpRequest();
   xhr.responseType = 'blob';
 
   xhr.onreadystatechange = function() {
     if (xhr.readyState != 4)
       return;
     if (xhr.status != 200) {
       onFailure(xhr.status);
       return;
     }
     var contentType = xhr.getResponseHeader('Content-Type');
     onSuccess(contentType, xhr.response);
   }.bind(this);
 
   // Perform a xhr request.
   try {
     xhr.open('GET', url, true);
-    xhr.setRequestHeader('Authorization', 'Bearer ' + token);
+    if (token)
+      xhr.setRequestHeader('Authorization', 'Bearer ' + token);
     xhr.send();
   } catch (e) {
     onFailure();
   }
+
+  return xhr;
 };
 
 /**
  * Sends the resized image via the callback. If the image has been changed,
  * then packs the canvas contents, otherwise sends the raw image data.
  *
  * @param {boolean} imageChanged Whether the image has been changed.
  * @private
  */
 Request.prototype.sendImage_ = function(imageChanged) {
@@ skipping 94 matching lines @@
   this.image_.src = 'data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAA' +
       'ABAAEAAAICTAEAOw==';
 
   this.xhr_.onload = function() {};
   this.xhr_.abort();
 
   // Dispose memory allocated by Canvas.
   this.canvas_.width = 0;
   this.canvas_.height = 0;
 };