Backed out changeset e00a268f35f3 (bug 1564738) for causing Bug 1753106 as requested by emk.

browser/base/content/tabbrowser.js

@@ -3070,11 +3070,10 @@
         this.removeTab(leftoverTab);
       }
 
-      TabBarVisibility.update();
-
       if (tabs.length > 1 || !tabs[0].selected) {
         this._updateTabsAfterInsert();
         this.tabContainer._setPositionalAttributes();
+        TabBarVisibility.update();
 
         for (let tab of tabs) {
           // If tabToSelect is a tab, we didn't reuse the selected tab.

browser/base/content/test/tabs/browser.ini

@@ -124,7 +124,6 @@ skip-if =
 [browser_tab_manager_visibility.js]
 [browser_tab_move_to_new_window_reload.js]
 [browser_tabCloseProbes.js]
-[browser_tabbar_visibility.js]
 [browser_tabContextMenu_keyboard.js]
 [browser_tabReorder_overflow.js]
 [browser_tabReorder.js]

browser/base/content/test/tabs/browser_tabbar_visibility.js

@@ -1,45 +0,0 @@
-/* Any copyright is dedicated to the Public Domain.
- * http://creativecommons.org/publicdomain/zero/1.0/ */
-
-"use strict";
-
-const { PromiseTestUtils } = ChromeUtils.import(
-  "resource://testing-common/PromiseTestUtils.jsm"
-);
-
-add_task(async function testWindowOpen() {
-  const DUMMY_PAGE = "browser/base/content/test/tabs/dummy_page.html";
-  const TEST_URL = "http://example.com/browser/" + DUMMY_PAGE;
-  const TEST_URL_CHROME = "chrome://mochitests/content/browser/" + DUMMY_PAGE;
-
-  BrowserTestUtils.loadURI(gBrowser.selectedBrowser, TEST_URL_CHROME);
-  await BrowserTestUtils.browserLoaded(gBrowser.selectedBrowser);
-
-  PromiseTestUtils.expectUncaughtRejection(/editor is null/); // bug 1752901
-  let newWindowPromise = BrowserTestUtils.waitForNewWindow({
-    url: TEST_URL,
-  });
-  await SpecialPowers.spawn(gBrowser.selectedBrowser, [TEST_URL], url => {
-    content.eval(`window.open("${url}", "_blank", "menubar=0")`);
-  });
-  let win = await newWindowPromise;
-
-  is(win.toolbar.visible, false, "toolbar should be hidden");
-  let toolbar = win.document.getElementById("TabsToolbar");
-  is(toolbar.collapsed, true, "tabbar should be collapsed");
-
-  await BrowserTestUtils.closeWindow(win);
-
-  PromiseTestUtils.expectUncaughtRejection(/editor is null/); // bug 1752901
-  newWindowPromise = BrowserTestUtils.waitForNewWindow({
-    url: TEST_URL,
-  });
-  SessionStore.undoCloseWindow(0);
-  win = await newWindowPromise;
-
-  is(win.toolbar.visible, false, "toolbar should be hidden");
-  toolbar = win.document.getElementById("TabsToolbar");
-  is(toolbar.collapsed, true, "tabbar should be collapsed");
-
-  await BrowserTestUtils.closeWindow(win);
-});