Bug 1360028 - Use getBoundsWithoutFlushing instead of getBoundingClientRect on addon-progress-notification to set the min-height of the addon-install-confirmation notifaction. r=willdurand

Differential Revision: https://phabricator.services.mozilla.com/D205455

browser/base/content/browser-addons.js

@@ -914,9 +914,9 @@ var gXPInstallObserver = {
           let height = undefined;
 
           if (PopupNotifications.isPanelOpen) {
-            let rect = document
-              .getElementById("addon-progress-notification")
-              .getBoundingClientRect();
+            let rect = window.windowUtils.getBoundsWithoutFlushing(
+              document.getElementById("addon-progress-notification")
+            );
             height = rect.height;
           }