fix(Cast): Allow serialize nested events (#9283)

Author: avelad

lib/cast/cast_utils.js

@@ -45,7 +45,7 @@ shaka.cast.CastUtils = class {
             } else if (eventValue instanceof Event ||
                   eventValue instanceof shaka.util.FakeEvent) {
               simpleEvent[eventKey] =
-                  shaka.cast.CastUtils.serialize(eventValue);
+                  shaka.cast.CastUtils.unpackEvent_(eventValue);
             } else if (isFakeEvent && Array.isArray(eventValue)) {
               simpleEvent[eventKey] = eventValue;
             }
@@ -124,6 +124,9 @@ shaka.cast.CastUtils = class {
       } else if (value && typeof value == 'object' &&
                  value['__type__'] == 'Error') {
         return shaka.cast.CastUtils.makeError_(value);
+      } else if (value && typeof value == 'object' &&
+                 value['__type__'] == 'Event') {
+        return shaka.cast.CastUtils.makeEvent_(value);
       }
       return value;
     });
@@ -199,6 +202,30 @@ shaka.cast.CastUtils = class {
   }
 
 
+  /**
+   * @param {!Object} value
+   * @return {!Object}
+   * @private
+   */
+  static unpackEvent_(value) {
+    return {
+      '__type__': 'Event',  // a signal to deserialize
+      'event': shaka.cast.CastUtils.serialize(value),
+    };
+  }
+
+
+  /**
+   * Creates a Event object from data sent by the cast receiver.
+   * @param {?} obj
+   * @return {!Object}
+   * @private
+   */
+  static makeEvent_(obj) {
+    return shaka.cast.CastUtils.deserialize(obj['event']);
+  }
+
+
   /**
    * @param {!Error} error
    * @return {!Object}