Allow mediaCast sender to run in background context

ext/src/shim/cast/classes/Session.ts

@@ -16,6 +16,8 @@ import { ErrorCode
        , SessionStatus
        , VolumeControlType } from "../enums";
 
+import { RepeatMode } from "../media/enums";
+
 import { ListenerObject
        , onMessage
        , sendMessageResponse } from "../../eventMessageChannel";
@@ -305,9 +307,10 @@ export default class Session {
           , autoplay: loadRequest.autoplay || false
           , currentTime: loadRequest.currentTime || 0
           , customData: loadRequest.customData || {}
-          , repeatMode: "REPEAT_OFF"
+          , repeatMode: RepeatMode.OFF
         });
 
+
         let hasResponded = false;
 
         this.addMessageListener(
@@ -318,23 +321,28 @@ export default class Session {
                 return;
             }
 
-            const mediaObject = JSON.parse(data);
+            const message = JSON.parse(data);
 
-            if (mediaObject.status && mediaObject.status.length > 0) {
+            if (message.status && message.status.length > 0) {
                 hasResponded = true;
 
                 const media = new Media(
                         this.sessionId
-                      , mediaObject.status[0].mediaSessionId
+                      , message.status[0].mediaSessionId
                       , _id.get(this));
 
                 media.media = loadRequest.media;
                 this.media = [ media ];
 
                 media.play();
-                successCallback(media);
+
+                if (successCallback) {
+                    successCallback(media);
+                }
             } else {
-                errorCallback(new _Error(ErrorCode.SESSION_ERROR));
+                if (errorCallback) {
+                    errorCallback(new _Error(ErrorCode.SESSION_ERROR));
+                }
             }
         });
     }

ext/src/shim/cast/index.ts

@@ -210,9 +210,6 @@ export function _requestSession (
 
     sessionRequestInProgress = true;
 
-    sessionSuccessCallback = successCallback;
-    sessionErrorCallback = errorCallback;
-
 
     const selectedReceiver = new Receiver_(
             _receiver.id
@@ -235,8 +232,8 @@ export function _requestSession (
 
                     sessionRequestInProgress = false;
 
-                    if (sessionSuccessCallback) {
-                        sessionSuccessCallback(session);
+                    if (successCallback) {
+                        successCallback(session);
                     }
                 }));
     }

ext/src/shim/cast/media/classes/Media.ts

@@ -293,7 +293,7 @@ export default class Media {
     }
 
 
-    private _sendMediaMessage (
+    public _sendMediaMessage (
             message: any
           , successCallback?: SuccessCallback
           , errorCallback?: ErrorCallback) {