Bug#840755: libwebkit2gtk-4.0-37: fails to play any youtube videos using flash plugin

[Sergio Villar Senin]

JFTR after some debugging we have verified that the problem is the VA-
API decoder not in webkitgtk

After enabling debug, we could see the following errors:

$ GST_DEBUG=3,webkit*:5 /usr/lib/x86_64-linux-gnu/webkit2gtk-
4.0/MiniBrowser
...
0x7fa5cc0f8770 ERROR       vaapivideomemory
gstvaapivideomemory.c:259:gst_video_meta_map_vaapi_memory: failed to
make image current0:00:33.398184225 23681 0x7fa5cc0f8770 ERROR         
      default video-frame.c:161:gst_video_frame_map_id: failed to map
video frame plane 0

That was confirmed later on by not whitelisting the VA-API module.

GST_PLUGIN_LOADING_WHITELIST="gstreamer:gst-plugins-base:gst-plugins-
good:gst-plugins-bad:gst-libav"

then the playback starts seamlessly.

BR