Bug 1880452 - Revert to recording FX_NEW_WINDOW_MS only when manually opening a new browser window from an existing one. r=mconley

Differential Revision: https://phabricator.services.mozilla.com/D204588

Author: daogottwald

browser/base/content/browser.js

@@ -4536,7 +4536,23 @@ function toOpenWindowByType(inType, uri, features) {
  * @return a reference to the new window.
  */
 function OpenBrowserWindow(options = {}) {
-  return BrowserWindowTracker.openWindow({ openerWindow: window, ...options });
+  let telemetryObj = {};
+  TelemetryStopwatch.start("FX_NEW_WINDOW_MS", telemetryObj);
+
+  let win = BrowserWindowTracker.openWindow({
+    openerWindow: window,
+    ...options,
+  });
+
+  win.addEventListener(
+    "MozAfterPaint",
+    () => {
+      TelemetryStopwatch.finish("FX_NEW_WINDOW_MS", telemetryObj);
+    },
+    { once: true }
+  );
+
+  return win;
 }
 
 /**

browser/modules/BrowserWindowTracker.sys.mjs

@@ -287,9 +287,6 @@ export const BrowserWindowTracker = {
     remote = undefined,
     fission = undefined,
   } = {}) {
-    let telemetryObj = {};
-    TelemetryStopwatch.start("FX_NEW_WINDOW_MS", telemetryObj);
-
     let windowFeatures = "chrome,dialog=no,all";
     if (features) {
       windowFeatures += `,${features}`;
@@ -344,7 +341,6 @@ export const BrowserWindowTracker = {
     win.addEventListener(
       "MozAfterPaint",
       () => {
-        TelemetryStopwatch.finish("FX_NEW_WINDOW_MS", telemetryObj);
         if (
           Services.prefs.getIntPref("browser.startup.page") == 1 &&
           loadURIString == lazy.HomePage.get()