Bug 1551855 - Add a dedicated pref for enabling GraphRunner. r=karlt

Differential Revision: https://phabricator.services.mozilla.com/D31262

--HG--
extra : moz-landing-system : lando

dom/media/MediaStreamGraph.cpp

@@ -3310,7 +3310,9 @@ MediaStreamGraph* MediaStreamGraph::GetInstance(
 
     GraphRunType runType = DIRECT_DRIVER;
     if (aGraphDriverRequested != OFFLINE_THREAD_DRIVER &&
-        Preferences::GetBool("dom.audioworklet.enabled", false)) {
+        (Preferences::GetBool("dom.audioworklet.enabled", false) ||
+         Preferences::GetBool("media.audiograph.single_thread.enabled",
+                              false))) {
       runType = SINGLE_THREAD;
     }
 

modules/libpref/init/all.js

@@ -623,6 +623,9 @@ pref("media.audioipc.stack_size", 262144);
 pref("media.cubeb.sandbox", false);
 #endif
 
+// GraphRunner (fixed MediaStreamGraph thread) control
+pref("media.audiograph.single_thread.enabled", false);
+
 #ifdef MOZ_AV1
 #if defined(XP_WIN) && !defined(_ARM64_)
 pref("media.av1.enabled", true);