Remove usage of DomDistillerService in ReadingListDownloadService.

ios/chrome/browser/reading_list/url_downloader_unittest.mm

 // 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 <vector>
 
 #include "base/files/file_util.h"
 #import "base/mac/bind_objc_block.h"
@@ skipping 11 matching lines @@
 namespace {
 
 class DistillerViewerTest : public dom_distiller::DistillerViewerInterface {
  public:
   DistillerViewerTest(const GURL& url,
                       const DistillationFinishedCallback& callback,
                       reading_list::ReadingListDistillerPageDelegate* delegate,
                       const std::string& html,
                       const GURL& redirect_url,
                       const std::string& mime_type)
-      : dom_distiller::DistillerViewerInterface(nil, nil) {
+      : dom_distiller::DistillerViewerInterface(nil) {
     std::vector<ImageInfo> images;
     if (redirect_url.is_valid()) {
       delegate->DistilledPageRedirectedToURL(url, redirect_url);
     }
     if (!mime_type.empty()) {
       delegate->DistilledPageHasMimeType(url, mime_type);
     }
     callback.Run(url, html, images, "title");
   }
 
@@ skipping 209 matching lines @@
   ASSERT_TRUE(std::find(downloader_->downloaded_files_.begin(),
                         downloader_->downloaded_files_.end(),
                         url) != downloader_->downloaded_files_.end());
   ASSERT_TRUE(std::find(downloader_->removed_files_.begin(),
                         downloader_->removed_files_.end(),
                         url) != downloader_->removed_files_.end());
   ASSERT_TRUE(downloader_->CheckExistenceOfOfflineURLPagePath(url));
 }
 
 }  // namespace