[FIX] mass_mailing: fixes save filter glitch

In the mass mailing form, when clicking on the filter save button, the screen
was unexpectedly scrolling down. This fixes this problem.

Task-2793090

closes odoo/odoo#86789

Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>

addons/mass_mailing/static/src/js/mailing_filter_widget.js

@@ -103,7 +103,7 @@ const FieldMailingFilter = FieldMany2One.extend({
     _onFavoriteFilterDropdownShown(ev) {
         const filterInput = ev.target.querySelector('input.o_mass_mailing_filter_name');
         filterInput.value = '';
-        filterInput.focus();
+        filterInput.focus({ preventScroll: true });
     },
 
     /**

addons/mass_mailing/static/tests/mass_mailing_favourite_filter_tests.js

@@ -151,6 +151,8 @@ QUnit.module('favorite filter widget', {
             "should have option to remove filter if filter is already set");
         assert.isNotVisible(form.$('.o_mass_mailing_save_filter_container'),
             "should not have option to save filter if filter is already set");
+        // Ensures input is not focussed otherwise clicking on it will just close the dropdown instead of opening it
+        form.$('.o_field_many2one[name="mailing_filter_id"] .o_input_dropdown input').blur();
         await testUtils.dom.click('.o_field_many2one[name="mailing_filter_id"] input');
         assert.containsN($dropdown, 'li.ui-menu-item', 2,
             "there should be two existing filters");