Bug 1782247 - Allow another rect for browser_windowopen.js. r=florian

Differential Revision: https://phabricator.services.mozilla.com/D153633

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

@@ -112,6 +112,18 @@ add_task(async function() {
             ) && // in the toolbar
             inRange(r.x1, 11, 13), // very close to the left of the screen
         },
+        {
+          name: "Initial favicon appearing after first paint",
+          condition: r => {
+            let faviconRect = win.gBrowser.tabs[0].iconImage.getBoundingClientRect();
+            return (
+              r.w == faviconRect.width &&
+              r.h == faviconRect.height &&
+              r.x1 == faviconRect.x &&
+              r.y1 == faviconRect.y
+            );
+          },
+        },
         {
           // Note that the length and x values here are a bit weird because on
           // some fonts, we appear to detect the two words separately.