Get signals working in the EXTRA_DATA section of MHTML

content/renderer/render_frame_impl.cc

Index: content/renderer/render_frame_impl.cc
diff --git a/content/renderer/render_frame_impl.cc b/content/renderer/render_frame_impl.cc
index e7d049c0d22cfd26f8f3ce455df2af10182aee9a..380a2cb7a1b0d88bd9ffea6582fcc33f97662d9f 100644
--- a/content/renderer/render_frame_impl.cc
+++ b/content/renderer/render_frame_impl.cc
@@ -5490,6 +5490,7 @@ void RenderFrameImpl::OnSerializeAsMHTML(
   const WebString mhtml_boundary =
       WebString::fromUTF8(params.mhtml_boundary_marker);
   DCHECK(!mhtml_boundary.isEmpty());
+  const std::vector<std::string> extra_data(params.extra_data);
 
   // Holds WebThreadSafeData instances for some or all of header, contents and
   // footer.
@@ -5528,6 +5529,24 @@ void RenderFrameImpl::OnSerializeAsMHTML(
     has_some_data |= !mhtml_contents.back().isEmpty();
   }
 
+  // Generate signal data (invisible) if needed, with mime-type SIGNAL_DATA
+  if (IsMainFrame() && extra_data.size() > 0) {
+    std::string data_string("\n");
+    data_string.append(mhtml_boundary.utf8());
+    // TODO(petewil): insert a mime type here instead of just a string
+    data_string.append("\nEXTRA_DATA\n");
+
+    for (const std::string& data : extra_data) {
+      data_string.append(data);
+      data_string.append("\n");
+    }
+
+    data_string.append(mhtml_boundary.utf8());
+    data_string.append("\n");
+    WebThreadSafeData mhtml_extra_data(data_string.c_str(), data_string.size());
+    mhtml_contents.emplace_back(mhtml_extra_data);
+  }
+
   // Generate MHTML footer if needed.
   if (save_status == MhtmlSaveStatus::SUCCESS && params.is_last_frame) {
     TRACE_EVENT0("page-serialization",