Bug 1356448: Allow software backed compositor process in nightly. r=dvander

--HG--
extra : rebase_source : f3fff5060b5bcc16c35fa10d5aec249f67cb0657

modules/libpref/init/all.js

@@ -4646,6 +4646,9 @@ pref("layers.bench.enabled", false);
 pref("layers.gpu-process.enabled", true);
 pref("layers.gpu-process.max_restarts", 3);
 pref("media.gpu-process-decoder", true);
+#ifdef NIGHTLY_BUILD
+pref("layers.gpu-process.allow-software", true);
+#endif
 #endif
 
 // Whether to force acceleration on, ignoring blacklists.