[fixup] Add minimal webrtcdesktopcapture api for hangout services extension

Change-Id: Ic681751fdb87414c9b9f4ebdbca91dc99515e184
Reviewed-on: https://codereview.qt-project.org/c/qt/qtwebengine-chromium/+/612722
Reviewed-by: Peter Varga <[email protected]>
(cherry picked from commit aaed201)
Reviewed-on: https://codereview.qt-project.org/c/qt/qtwebengine-chromium/+/613020
Reviewed-by: Qt Cherry-pick Bot <[email protected]>

Author: Allan Sandfeld Jensen

chromium/qtwebengine/browser/extensions/api/webrtc_desktop_capture_private/webrtc_desktop_capture_private_api.cc

@@ -90,7 +90,7 @@ WebrtcDesktopCapturePrivateChooseDesktopMediaFunction::Run() {
                                                             request_id_, this);
   mutable_args().erase(args().begin());
 
-  absl::optional<Params> params = Params::Create(args());
+  std::optional<Params> params = Params::Create(args());
   EXTENSION_FUNCTION_VALIDATE(params);
 
   content::RenderFrameHost* rfh = content::RenderFrameHost::FromID(