[epiphany] Canary: Enable internal WebKit audio mixer

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

commit cb79ab1b0841474cafbdfa00c1be082ff19f45f4
Author: Philippe Normand <philn igalia com>
Date:   Fri Dec 3 17:42:42 2021 +0000

    Canary: Enable internal WebKit audio mixer
    
    With this enabled, each ephy tab will maintain a single connection to PA/PW. In
    the GNOME audio settings if an ephy tab is playing more than one audio stream it
    will thus be listed once, instead of one time per media element or WebAudio
    session.
    
    This is an experimental feature, reverse playback is not supported yet.
    
    Part-of: <https://gitlab.gnome.org/GNOME/epiphany/-/merge_requests/1039>

 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 bc6984838..20bbb8e4a 100644
--- a/org.gnome.Epiphany.Canary.json.in
+++ b/org.gnome.Epiphany.Canary.json.in
@@ -204,6 +204,7 @@
                     "commands" : [
                         "export WEBKIT_INJECTED_BUNDLE_PATH=/app/lib",
                         "export WEBKIT_EXEC_PATH=/app/libexec",
+                        "export WEBKIT_GST_ENABLE_AUDIO_MIXER=1",
                         "exec epiphany \"$@\""
                     ]
                 }