Document extension messages and remove unnecessary messages/message data

ext/src/cast/export.ts

@@ -97,9 +97,7 @@ export function ensureInit(): Promise<TypedMessagePort<Message>> {
         function handleIncomingMessageToCast(message: Message) {
             switch (message.subject) {
                 case "cast:initialized": {
-                    initializedBridgeInfo = message.data;
-
-                    if (initializedBridgeInfo.isVersionCompatible) {
+                    if (message.data.isAvailable) {
                         resolve(initializedBackgroundPort);
                     } else {
                         reject();

ext/src/cast/index.ts

@@ -49,7 +49,7 @@ eventMessaging.page.addListener(async message => {
             // Call page script/framework API script's init function
             const initFn = _window.__onGCastApiAvailable;
             if (initFn && typeof initFn === "function") {
-                initFn(message.data.isVersionCompatible);
+                initFn(message.data.isAvailable);
             }
 
             break;

ext/src/cast/sdk/index.ts

@@ -143,11 +143,6 @@ export default class {
              * and data needed to create cast API objects is sent.
              */
             case "cast:sessionCreated": {
-                // Notify background to close UI
-                eventMessaging.page.sendMessage({
-                    subject: "main:closeReceiverSelector"
-                });
-
                 const status = message.data;
                 const receiverDevice = this.#receiverDevices.get(
                     status.receiverId