Check bridge compat before initializing cast shim

ext/src/shim/index.js

@@ -1,18 +1,35 @@
-"use strict";
-
-import cast  from "./cast";
-import media from "./media";
-
-if (!window.chrome) {
-	window.chrome = {};
-}
-
-window.chrome.cast = cast;
-window.chrome.cast.media = media;
-
-// Call page's API loaded function if defined
-const readyFunction = window.__onGCastApiAvailable;
-console.log(readyFunction);
-if (readyFunction && typeof readyFunction === "function") {
-    readyFunction(true);
-}
+"use strict";
+
+import cast  from "./cast";
+import media from "./media";
+
+import { onMessage, sendMessage } from "./messageBridge";
+
+
+if (!window.chrome) {
+	window.chrome = {};
+}
+
+window.chrome.cast = cast;
+window.chrome.cast.media = media;
+
+
+onMessage(message => {
+    switch (message.subject) {
+        case "shim:initialized": {
+            const bridgeInfo = message.data;
+
+            // Call page's API loaded function if defined
+            const readyFunction = window.__onGCastApiAvailable;
+            if (readyFunction && typeof readyFunction === "function") {
+                readyFunction(bridgeInfo && bridgeInfo.isVersionCompatible);
+            }
+            break;
+        };
+    }
+});
+
+// Trigger bridge mDNS discovery
+sendMessage({
+    subject: "main:initialize"
+});