[epiphany] Canary: Enable the new libva GStreamer decoders

[Marge Bot <marge-bot src gnome org>]

commit c383d83ac1c74a0ecc869516e8cc4a9206848312
Author: Philippe Normand <philn igalia com>
Date:   Mon Apr 11 13:01:48 2022 +0100

    Canary: Enable the new libva GStreamer decoders
    
    The WebKit SDK now ships the gstva plugin, which aims to be a replacement for
    gstreamer-vaapi. The elements are currently down-ranked but should be usable,
    testing was performed on a machine with a Radeon rx 560 GPU, but should also
    work on Intel GPUs (YMMV).
    
    Part-of: <https://gitlab.gnome.org/GNOME/epiphany/-/merge_requests/1105>

 org.gnome.Epiphany.Canary.json.in | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/org.gnome.Epiphany.Canary.json.in b/org.gnome.Epiphany.Canary.json.in
index 299af7304..0619da331 100644
--- a/org.gnome.Epiphany.Canary.json.in
+++ b/org.gnome.Epiphany.Canary.json.in
@@ -140,6 +140,7 @@
                         "export WEBKIT_INJECTED_BUNDLE_PATH=/app/lib",
                         "export WEBKIT_EXEC_PATH=/app/libexec",
                         "export WEBKIT_GST_ENABLE_AUDIO_MIXER=1",
+                        "export 
GST_PLUGIN_FEATURE_RANK=vah264dec:MAX,vah265dec:MAX,vavp8dec:MAX,vavp9dec:MAX",
                         "exec epiphany \"$@\""
                     ]
                 }