Add a focus_composer dispatcher action

and use it

src/components/views/elements/ReplyThread.js

@@ -26,6 +26,7 @@ import {makeUserPermalink, RoomPermalinkCreator} from "../../../utils/permalinks
 import SettingsStore from "../../../settings/SettingsStore";
 import escapeHtml from "escape-html";
 import MatrixClientContext from "../../../contexts/MatrixClientContext";
+import {Action} from "../../../dispatcher/actions";
 
 // This component does no cycle detection, simply because the only way to make such a cycle would be to
 // craft event_id's, using a homeserver that generates predictable event IDs; even then the impact would
@@ -290,7 +291,7 @@ export default class ReplyThread extends React.Component {
             events,
         }, this.loadNextEvent);
 
-        dis.dispatch({action: 'focus_composer'});
+        dis.fire(Action.FocusComposer);
     }
 
     render() {