Bug 1553593 - Allow the searchplugins stat call to happen later with WebRender. r=florian

Differential Revision: https://phabricator.services.mozilla.com/D32471

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

browser/base/content/test/performance/browser_startup_mainthreadio.js

@@ -530,6 +530,7 @@ const startupPhases = {
     { // bug 1003968
       path: "XREAppDist:searchplugins",
       condition: WIN,
+      ignoreIfUnused: true, // with WebRender enabled this may happen during "before becoming idle"
       stat: 1,
     },
     {
@@ -643,6 +644,12 @@ const startupPhases = {
       condition: WIN,
       stat: 7,
     },
+    { // bug 1003968
+      path: "XREAppDist:searchplugins",
+      condition: WIN,
+      ignoreIfUnused: true, // with WebRender enabled this may happen during "before handling user events"
+      stat: 1,
+    },
   ],
 };