[FIX] web: fix form view "More" button

In form views, when the window size is too small, a "More" button
appears and it should contain the overflow buttons.

On all browsers, the "More" dropdown doesn't contain the expected
amount of buttons, so it is shifted on the second line.

Before this commit:

    - The "More" dropdown doesn't contain the expected amount of
      buttons, so it is shifted on the second line.

After this commit:

    - The "More" dropdown contains the expected amount of buttons
      and it is not shifted on the second line anymore.

OPW-2079694

X-original-commit: f04f67e

addons/web/static/src/js/views/form/form_renderer.js

@@ -457,7 +457,7 @@ var FormRenderer = BasicRenderer.extend({
     * @returns {integer}
     */
     _renderButtonBoxNbButtons: function () {
-        return [2, 2, 4, 6][config.device.size_class] || 7;
+        return [2, 2, 2, 4][config.device.size_class] || 7;
     },
     /**
      * @private

addons/web/static/tests/views/form_tests.js

@@ -5091,6 +5091,49 @@ QUnit.module('Views', {
         form.destroy();
     });
 
+    QUnit.test('correct amount of buttons', async function (assert) {
+        assert.expect(7);
+
+        var self = this;
+        var buttons = Array(8).join(
+            '<button type="object" class="oe_stat_button" icon="fa-check-square">' +
+                '<field name="bar"/>' +
+            '</button>'
+        );
+        var statButtonSelector = '.oe_stat_button:not(.dropdown-item, .dropdown-toggle)';
+
+        var createFormWithDeviceSizeClass = async function (size_class) {
+            return await createView({
+                View: FormView,
+                model: 'partner',
+                data: self.data,
+                arch: '<form>' +
+                    '<div name="button_box" class="oe_button_box">'
+                        + buttons +
+                    '</div>' +
+                '</form>',
+                res_id: 2,
+                config: {
+                    device: {size_class: size_class},
+                },
+            });
+        }
+
+        var assertFormContainsNButtonsWithSizeClass = async function (size_class, n) {
+            var form = await createFormWithDeviceSizeClass(size_class);
+            assert.containsN(form, statButtonSelector, n, 'The form has the expected amount of buttons');
+            form.destroy();
+        }
+
+        await assertFormContainsNButtonsWithSizeClass(0, 2);
+        await assertFormContainsNButtonsWithSizeClass(1, 2);
+        await assertFormContainsNButtonsWithSizeClass(2, 2);
+        await assertFormContainsNButtonsWithSizeClass(3, 4);
+        await assertFormContainsNButtonsWithSizeClass(4, 7);
+        await assertFormContainsNButtonsWithSizeClass(5, 7);
+        await assertFormContainsNButtonsWithSizeClass(6, 7);
+    });
+
     QUnit.module('focus and scroll test', async function () {
         QUnit.test('no focus set on form when closing many2one modal if lastActivatedFieldIndex is not set', async function (assert) {
             assert.expect(8);