Expose mixin for inheritance, fix some spacing.

Related to https://github.com/OCA/web/pull/481.

web_x2many_delete_all/static/src/js/web_x2many_delete_all.js

@@ -1,10 +1,9 @@
 /* Copyright 2016 Onestein
  * License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl). */
 
-odoo.define('web_x2many_delete_all', function (require) {
-"use strict";
-    var core = require('web.core'),
-        _t = core._t;
+odoo.define('web_x2many_delete_all.Mixin', function (require) {
+    "use strict";
+    var core = require('web.core');
 
     var X2ManyListDeleteAllMixin = {
         events: {
@@ -19,14 +18,14 @@ odoo.define('web_x2many_delete_all', function (require) {
             return res
         },
         toggle_btn_delete_all: function() {
-            if(this.get('effective_readonly')) {
+            if (this.get('effective_readonly')) {
                 this.$('th.o_list_record_delete > .fa-trash-o').addClass('hidden');
             } else {
                 this.$('th.o_list_record_delete > .fa-trash-o').removeClass('hidden');
             }
         },
         btn_delete_all_clicked: function() {
-            if(this.get('effective_readonly')) return;
+            if (this.get('effective_readonly')) return;
             this.delete_all();
         },
         delete_all: function() {
@@ -36,4 +35,6 @@ odoo.define('web_x2many_delete_all', function (require) {
 
     core.form_widget_registry.get('many2many').include(X2ManyListDeleteAllMixin);
     core.form_widget_registry.get('one2many').include(X2ManyListDeleteAllMixin);
+
+    return X2ManyListDeleteAllMixin;
 });