WPE external holepunch test

This test checks whether the external holepunch feature is working on WPE.

There is a video player of 400x400 below this text. It will play a valid video for 5 seconds, then a holepunch one for another 5 seconds and then the first one again.

If everything is working fine, there should be the valid video for 5 seconds, then a transparent rectangle of 400x400 for 5 seconds, and then again the valid video.

If GStreamer holepunch is enabled when running this test, the first and third video will show a transparent rectangle instead of the video content.