Remove all ReadingList entries on managed account signout.

ios/chrome/browser/reading_list/url_downloader.cc

 // 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.
 
 #include "ios/chrome/browser/reading_list/url_downloader.h"
 
 #include <string>
 #include <vector>
 
 #include "base/files/file_path.h"
@@ skipping 201 matching lines @@
   fetcher_->GetResponseAsFilePath(false, &temporary_path);
 
   task_tracker_.PostTaskAndReplyWithResult(
       web::WebThread::GetTaskRunnerForThread(web::WebThread::FILE).get(),
       FROM_HERE, base::Bind(&URLDownloader::SavePDFFile, base::Unretained(this),
                             temporary_path),
       base::Bind(&URLDownloader::DownloadCompletionHandler,
                  base::Unretained(this), source->GetOriginalURL(), "", path));
 }
 
+void URLDownloader::CancelTask() {
+  task_tracker_.TryCancelAll();
+  distiller_.reset();
+}
+
 void URLDownloader::FetchPDFFile() {
   const GURL& pdf_url =
       distilled_url_.is_valid() ? distilled_url_ : original_url_;
   fetcher_ = net::URLFetcher::Create(0, pdf_url, net::URLFetcher::GET, this);
   fetcher_->SetRequestContext(url_request_context_getter_.get());
   fetcher_->SetLoadFlags(net::LOAD_SKIP_CACHE_VALIDATION);
   fetcher_->SaveResponseToTemporaryFile(
       web::WebThread::GetTaskRunnerForThread(web::WebThread::FILE));
   fetcher_->Start();
 }
@@ skipping 140 matching lines @@
   base::FilePath path = reading_list::OfflineURLAbsolutePathFromRelativePath(
       base_directory_,
       reading_list::OfflinePagePath(url, reading_list::OFFLINE_TYPE_HTML));
   int written = base::WriteFile(path, html.c_str(), html.length());
   if (written <= 0) {
     return false;
   }
   saved_size_ += written;
   return true;
 }