Add a display_id parameter to the desktopCapturer API. (#12417)

* Add a screen_api_id parameter to the desktopCapturer API.

When using the DirectX capturer on Windows, there was previously no way
to associate desktopCapturer/getUserMedia and electron.screen API
screens. This new parameter provides the association.

* Fix non-Windows build.

* Fix Mac.

* Fix Mac harder.

* JS lint

* clang-format C++ code.

* IWYU

* display_id, Linux comment, better test

* lint

* Fix tests on Linux.

* Add display_id documentation.

lib/browser/desktop-capturer.js

@@ -43,7 +43,8 @@ desktopCapturer.emit = (event, name, sources) => {
     return {
       id: source.id,
       name: source.name,
-      thumbnail: source.thumbnail.toDataURL()
+      thumbnail: source.thumbnail.toDataURL(),
+      display_id: source.display_id
     }
   })