ref(api): move tile view subscriber to api dir

react/features/external-api/index.js

@@ -1 +1,2 @@
 import './middleware';
+import './subscriber';

react/features/external-api/subscriber.js

@@ -0,0 +1,16 @@
+// @flow
+
+import { StateListenerRegistry } from '../base/redux';
+import { shouldDisplayTileView } from '../video-layout';
+
+declare var APP: Object;
+
+/**
+ * StateListenerRegistry provides a reliable way of detecting changes to
+ * preferred layout state and dispatching additional actions.
+ */
+StateListenerRegistry.register(
+    /* selector */ state => shouldDisplayTileView(state),
+    /* listener */ displayTileView => {
+        APP.API.notifyTileViewChanged(displayTileView);
+    });

react/features/video-layout/subscriber.js

@@ -36,10 +36,6 @@ StateListenerRegistry.register(
                 _updateAutoPinnedParticipant(store);
             }
         }
-
-        if (typeof APP === 'object') {
-            APP.API.notifyTileViewChanged(displayTileView);
-        }
     }
 );