Bug 1658342 - Enable the remoteObjectEmbed pref by default, r=heycam,valentin

This also disables the cross-origin resource timing test when Fission is
enabled, as resource timing is is broken for cross-origin frames (bug 1658097).

Differential Revision: https://phabricator.services.mozilla.com/D91326

dom/tests/mochitest/general/mochitest.ini

@@ -119,6 +119,7 @@ skip-if = verify
 [test_resource_timing.html]
 skip-if = verify
 [test_resource_timing_cross_origin.html]
+skip-if = fission # bug 1658097
 [test_resource_timing_frameset.html]
 [test_selectevents.html]
 skip-if = toolkit == 'android' # bug 1627523

modules/libpref/init/StaticPrefList.yaml

@@ -3602,7 +3602,7 @@
 # `useRemoteSubframes` flag set.
 - name: fission.remoteObjectEmbed
   type: bool
-  value: false
+  value: true
   mirror: always
 
 #---------------------------------------------------------------------------