Get signals working in the EXTRA_DATA section of MHTML

chrome/browser/android/offline_pages/offline_page_mhtml_archiver.h

Index: chrome/browser/android/offline_pages/offline_page_mhtml_archiver.h
diff --git a/chrome/browser/android/offline_pages/offline_page_mhtml_archiver.h b/chrome/browser/android/offline_pages/offline_page_mhtml_archiver.h
index 59272ad5ec4d1d20f5626c21a10d22d61271465a..a51407a9a3f168bbbb2a79b98973df8c3ee28c75 100644
--- a/chrome/browser/android/offline_pages/offline_page_mhtml_archiver.h
+++ b/chrome/browser/android/offline_pages/offline_page_mhtml_archiver.h
@@ -49,6 +49,7 @@ class OfflinePageMHTMLArchiver : public OfflinePageArchiver {
   // OfflinePageArchiver implementation:
   void CreateArchive(const base::FilePath& archives_dir,
                      const CreateArchiveParams& create_archive_params,
+                     const std::string& signal_data,
                      const CreateArchiveCallback& callback) override;
 
  protected:
@@ -78,6 +79,11 @@ class OfflinePageMHTMLArchiver : public OfflinePageArchiver {
   // Contents of the web page to be serialized. Not owned.
   content::WebContents* web_contents_;
 
+  // Saved signal data corresponding to this page load. This is a way of logging
+  // signals that have been received as of the time of the page capture to help
+  // training a recognizer for when to take a snapshot.
+  std::string signal_data_;
+
   CreateArchiveCallback callback_;
 
   base::WeakPtrFactory<OfflinePageMHTMLArchiver> weak_ptr_factory_;