Focus search text input when opening "Direct Messages" modal (#3231)

webapp/components/filtered_user_list.jsx

@@ -52,6 +52,10 @@ class FilteredUserList extends React.Component {
         }
     }
 
+    componentDidMount() {
+        ReactDOM.findDOMNode(this.refs.filter).focus();
+    }
+
     componentDidUpdate(prevProps, prevState) {
         if (prevState.filter !== this.state.filter) {
             $(ReactDOM.findDOMNode(this.refs.userList)).scrollTop(0);