--- a/browser/base/content/test/performance/browser_windowopen_reflows.js
+++ b/browser/base/content/test/performance/browser_windowopen_reflows.js
@@ -7,24 +7,17 @@
  * WHOA THERE: We should never be adding new things to EXPECTED_REFLOWS. This
  * is a whitelist that should slowly go away as we improve the performance of
  * the front-end. Instead of adding more reflows to the whitelist, you should
  * be modifying your code to avoid the reflow.
  *
  * See https://developer.mozilla.org/en-US/Firefox/Performance_best_practices_for_Firefox_fe_engineers
  * for tips on how to do that.
  */
-const EXPECTED_REFLOWS = [
-  {
-    stack: [
-      "select@chrome://global/content/bindings/textbox.xml",
-      "focusAndSelectUrlBar@chrome://browser/content/browser.js",
-    ],
-  },
-];
+const EXPECTED_REFLOWS = [];
 
 if (Services.appinfo.OS == "WINNT") {
   EXPECTED_REFLOWS.push(
     {
       stack: [
         "verticalMargins@chrome://browser/content/browser-tabsintitlebar.js",
         "_update@chrome://browser/content/browser-tabsintitlebar.js",
         "init@chrome://browser/content/browser-tabsintitlebar.js",
@@ -34,16 +27,22 @@ if (Services.appinfo.OS == "WINNT") {
     },
   );
 }
 
 if (Services.appinfo.OS == "WINNT" || Services.appinfo.OS == "Darwin") {
   EXPECTED_REFLOWS.push(
     {
       stack: [
+        "select@chrome://global/content/bindings/textbox.xml",
+        "focusAndSelectUrlBar@chrome://browser/content/browser.js",
+      ],
+    },
+    {
+      stack: [
         "rect@chrome://browser/content/browser-tabsintitlebar.js",
         "_update@chrome://browser/content/browser-tabsintitlebar.js",
         "init@chrome://browser/content/browser-tabsintitlebar.js",
         "handleEvent@chrome://browser/content/tabbrowser.xml",
       ],
       times: 4, // This number should only ever go down - never up.
     },
   );

--- a/browser/base/content/test/performance/head.js
+++ b/browser/base/content/test/performance/head.js
@@ -139,24 +139,28 @@ async function withReflowObserver(testFn
   docShell.addWeakReflowObserver(observer);
 
   Services.els.addListenerForAllEvents(win, dirtyFrameFn, true);
 
   try {
     dirtyFrameFn();
     await testFn(dirtyFrameFn);
   } finally {
-    for (let remainder of expectedReflows) {
-      if (!Number.isInteger(remainder.minTimes) || remainder.minTimes > 0) {
-        Assert.ok(false,
-                  `Unused expected reflow: ${JSON.stringify(remainder.stack, null, "\t")}\n` +
-                  `This reflow was supposed to be hit ${remainder.minTimes || remainder.times} more time(s).\n` +
-                  "This is probably a good thing - just remove it from the " +
-                  "expected list.");
+    if (expectedReflows.length != 0) {
+      for (let remainder of expectedReflows) {
+        if (!Number.isInteger(remainder.minTimes) || remainder.minTimes > 0) {
+          Assert.ok(false,
+                    `Unused expected reflow: ${JSON.stringify(remainder.stack, null, "\t")}\n` +
+                    `This reflow was supposed to be hit ${remainder.minTimes || remainder.times} more time(s).\n` +
+                    "This is probably a good thing - just remove it from the " +
+                    "expected list.");
+        }
       }
+    } else {
+      Assert.ok(true, "All expected reflows were observed");
     }
 
     Services.els.removeListenerForAllEvents(win, dirtyFrameFn, true);
     docShell.removeWeakReflowObserver(observer);
   }
 }
 
 async function ensureNoPreloadedBrowser() {