fix bug 1415050 to work with 2.57

rel-257/libdav1d/patches/1417050-2-63a1.patch

@@ -381,3 +381,24 @@ diff --git a/dom/media/test/test_can_play_type_mpeg.html b/dom/media/test/test_c
      is(v.canPlayType(type), ex, type + "='" + ex + "'");
    }
  
+diff --git a/testing/profiles/prefs_general.js b/testing/profiles/prefs_general.js
+--- a/testing/profiles/prefs_general.js
++++ b/testing/profiles/prefs_general.js
+@@ -40,16 +40,17 @@ user_pref("gfx.color_management.force_sr
+ user_pref("gfx.logging.level", 1);
+ user_pref("network.manage-offline-status", false);
+ // Disable speculative connections so they aren't reported as leaking when they're hanging around.
+ user_pref("network.http.speculative-parallel-limit", 0);
+ user_pref("dom.min_background_timeout_value", 1000);
+ user_pref("test.mousescroll", true);
+ user_pref("security.default_personal_cert", "Select Automatically"); // Need to client auth test be w/o any dialogs
+ user_pref("network.http.prompt-temp-redirect", false);
++user_pref("media.av1.enabled", true);
+ user_pref("media.preload.default", 2); // default = metadata
+ user_pref("media.preload.auto", 3); // auto = enough
+ user_pref("media.cache_size", 1000);
+ user_pref("media.memory_cache_max_size", 32);
+ user_pref("media.memory_caches_combined_limit_kb", 256);
+ user_pref("media.volume_scale", "0.01");
+ user_pref("media.test.dumpDebugInfo", true);
+ user_pref("media.dormant-on-pause-timeout-ms", 0); // Enter dormant immediately without waiting for timeout.