Added preference_changed web socket event

web/react/stores/socket_store.jsx

@@ -135,6 +135,10 @@ class SocketStoreClass extends EventEmitter {
             handleChannelViewedEvent(msg);
             break;
 
+        case SocketEvents.PREFERENCE_CHANGED:
+            handlePreferenceChangedEvent(msg);
+            break;
+
         default:
         }
     }
@@ -279,6 +283,11 @@ function handleChannelViewedEvent(msg) {
     }
 }
 
+function handlePreferenceChangedEvent(msg) {
+    const preference = JSON.parse(msg.props.preference);
+    EventHelpers.emitPreferenceChangedEvent(preference);
+}
+
 var SocketStore = new SocketStoreClass();
 
 /*SocketStore.dispatchToken = AppDispatcher.register((payload) => {