Bug 1637012 - Set devtools.browsertoolbox.fission to true in browser_resources_several_resources.js r=nchevobbe

Differential Revision: https://phabricator.services.mozilla.com/D74828

devtools/shared/resources/tests/browser_resources_several_resources.js

@@ -12,6 +12,12 @@ const {
  * after unwatching one resource, if there is still another watched resource.
  */
 add_task(async function() {
+  // We will create a main process target list here in order to monitor
+  // resources from new tabs as they get created.
+  // devtools.browsertoolbox.fission should be true to monitor resources from
+  // remote browsers & frames.
+  await pushPref("devtools.browsertoolbox.fission", true);
+
   // Open a test tab
   gBrowser.selectedTab = BrowserTestUtils.addTab(gBrowser);
   const tab = await addTab("data:text/html,Root Node tests");