[Solved]-Customizing the Stockchart range selector buttons from HighCharts library in GWT (and Javascript in general)-Highcharts

Could you please try following:

 String rangeSelectorConfig =  " {\n" +
            "                buttons: [{\n" +
            "                    type: 'day',\n" +
            "                    count: 3,\n" +
            "                    text: '3dias'\n" +
            "                }, {\n" +
            "                    type: 'week',\n" +
            "                    count: 1,\n" +
            "                    text: '1w'\n" +
            "                }]" +
            "            }" ;
 JSONValue config = JSONParser.parseLenient(rangeSelectorConfig);
 chart.setOption("/rangeSelector", config);

Chart class (with help of Configurable) doesn't parse JSON objects for you, so buttons in your code were passed as string literals to native HightCharts JS.