Get signals working in the EXTRA_DATA section of MHTML

chrome/browser/android/offline_pages/recent_tab_helper.cc

 // Copyright (c) 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 "chrome/browser/android/offline_pages/recent_tab_helper.h"
 
 #include <queue>
 #include <vector>
 
 #include "base/bind.h"
@@ skipping 385 matching lines @@
   DCHECK(OfflinePageModel::CanSaveURL(web_contents()->GetLastCommittedURL()));
   snapshot_info->expected_page_quality =
       snapshot_controller_->current_page_quality();
   OfflinePageModel::SavePageParams save_page_params;
   save_page_params.url = web_contents()->GetLastCommittedURL();
   save_page_params.client_id = snapshot_info->client_id;
   save_page_params.proposed_offline_id = snapshot_info->request_id;
   save_page_params.is_background = false;
   save_page_params.original_url =
       OfflinePageUtils::GetOriginalURLFromWebContents(web_contents());
+  std::string signal_data;
   page_model_->SavePage(
       save_page_params, delegate_->CreatePageArchiver(web_contents()),
+      signal_data,
       base::Bind(&RecentTabHelper::SavePageCallback,
                  weak_ptr_factory_.GetWeakPtr(), snapshot_info));
 }
 
 void RecentTabHelper::SavePageCallback(SnapshotProgressInfo* snapshot_info,
                                        OfflinePageModel::SavePageResult result,
                                        int64_t offline_id) {
   DCHECK(snapshot_info->IsForLastN() ||
          snapshot_info->request_id == offline_id);
   ReportSnapshotCompleted(snapshot_info, result == SavePageResult::SUCCESS);
@@ skipping 56 matching lines @@
 }
 
 void RecentTabHelper::CancelInFlightSnapshots() {
   weak_ptr_factory_.InvalidateWeakPtrs();
   downloads_ongoing_snapshot_info_.reset();
   downloads_latest_saved_snapshot_info_.reset();
   last_n_ongoing_snapshot_info_.reset();
 }
 
 }  // namespace offline_pages