Get signals working in the EXTRA_DATA section of MHTML

chrome/browser/android/offline_pages/offline_page_mhtml_archiver.cc

Index: chrome/browser/android/offline_pages/offline_page_mhtml_archiver.cc
diff --git a/chrome/browser/android/offline_pages/offline_page_mhtml_archiver.cc b/chrome/browser/android/offline_pages/offline_page_mhtml_archiver.cc
index 27948ae0aa02652fe93f6c0ba118d6737a6b37ca..a598256dd01c6c17119208ed8807a8862900ba2f 100644
--- a/chrome/browser/android/offline_pages/offline_page_mhtml_archiver.cc
+++ b/chrome/browser/android/offline_pages/offline_page_mhtml_archiver.cc
@@ -53,10 +53,12 @@ OfflinePageMHTMLArchiver::~OfflinePageMHTMLArchiver() {
 void OfflinePageMHTMLArchiver::CreateArchive(
     const base::FilePath& archives_dir,
     const CreateArchiveParams& create_archive_params,
+    const std::string& signal_data,
     const CreateArchiveCallback& callback) {
   DCHECK(callback_.is_null());
   DCHECK(!callback.is_null());
   callback_ = callback;
+  signal_data_ = signal_data;
 
   if (HasConnectionSecurityError()) {
     ReportFailure(ArchiverResult::ERROR_SECURITY_CERTIFICATE);
@@ -97,6 +99,7 @@ void OfflinePageMHTMLArchiver::GenerateMHTML(
   content::MHTMLGenerationParams params(file_path);
   params.use_binary_encoding = true;
   params.remove_popup_overlay = create_archive_params.remove_popup_overlay;
+  params.extra_data = signal_data_;
 
   web_contents_->GenerateMHTML(
       params,