Bug 989289 - Forcibly set the 'mode' attribute to 'icons' on toolbar construction. r=jaws.

browser/components/customizableui/content/toolbar.xml

@@ -45,6 +45,11 @@
           Cu.import("resource:///modules/CustomizableUI.jsm", scope);
           let CustomizableUI = scope.CustomizableUI;
 
+          // Bug 989289: Forcibly set the now unsupported "mode" attribute, just
+          // in case it gets accidentally restored from persistence from a user
+          // that's been upgrading and downgrading.
+          this.setAttribute("mode", "icons");
+
           // Searching for the toolbox palette in the toolbar binding because
           // toolbars are constructed first.
           let toolbox = this.toolbox;

browser/components/customizableui/test/browser.ini

@@ -94,4 +94,5 @@ skip-if = os == "linux"
 [browser_987177_destroyWidget_xul.js]
 [browser_987177_xul_wrapper_updating.js]
 [browser_987492_window_api.js]
+[browser_989289_force_icons_mode_attribute.js]
 [browser_panel_toggle.js]

browser/components/customizableui/test/browser_989289_force_icons_mode_attribute.js

@@ -0,0 +1,31 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const kToolbarID = "test-toolbar";
+
+/**
+ * Tests that customizable toolbars are forced to have their mode
+ * attribute set to "icons".
+ */
+add_task(function* testAddingToolbar() {
+  let toolbar = document.createElement("toolbar");
+  toolbar.setAttribute("mode", "full");
+  toolbar.setAttribute("customizable", "true");
+  toolbar.setAttribute("id", kToolbarID);
+
+  CustomizableUI.registerArea(kToolbarID, {
+     type: CustomizableUI.TYPE_TOOLBAR,
+     legacy: false,
+  })
+
+  gNavToolbox.appendChild(toolbar);
+
+  is(toolbar.getAttribute("mode"), "icons",
+     "Toolbar should have its mode attribute set to icons.")
+
+  toolbar.remove();
+  CustomizableUI.unregisterArea(kToolbarID);
+});