[FIX] web: fix Groupby menu style in embedded graph views

addons/web/static/src/js/views/control_panel/search/groupby_menu_mixin.js

@@ -36,6 +36,7 @@ var GroupByMenuMixin = {
      * private
      * @param {jQuery} $node
      * @param {Object} groupableFields
+     * @param {Promise}
      */
     _addGroupByMenu: function ($node, groupableFields) {
         this.sortedFieldNames = _.sortBy(Object.keys(groupableFields), function (fieldName) {
@@ -44,7 +45,7 @@ var GroupByMenuMixin = {
         this.groupableFields = groupableFields;
         var groupBys = this._getGroupBys(this.model.get().groupBy);
         this.groupByMenu = new GroupByMenu(this, groupBys, this.groupableFields);
-        this.groupByMenu.insertAfter($node.find('div:first'));
+        return this.groupByMenu.insertAfter($node.find('div:first'));
     },
     /**
      * This method puts the active groupBys in a convenient form.

addons/web/static/src/js/views/graph/graph_controller.js

@@ -96,8 +96,13 @@ var GraphController = AbstractController.extend(GroupByMenuMixin,{
             this._updateButtons();
             this.$buttons.appendTo($node);
             if (this.isEmbedded) {
-                this._addGroupByMenu($node, this.groupableFields);
+                this._addGroupByMenu($node, this.groupableFields).then(function(){
+                    var groupByButton = $node.find('.o_dropdown_toggler_btn');
+                    groupByButton.removeClass("o_dropdown_toggler_btn btn btn-secondary dropdown-toggle");
+                    groupByButton.addClass("btn dropdown-toggle btn-outline-secondary");
+                });
             }
+
         }
     },