otifying MediaKeySystemAccess.
  // @param aTopic should be "mediakeys-request".
  // @param aData json containing a `status` and a `keysystem`.
  observe(aSubject, aTopic, aData) {
    let parsedData;
    try {
      parsedData = JSON.parse(aData);
    } catch (ex) {
      console.error("Malformed EME video message with data: ", aData);
      return;
    }
    const { status } = parsedData;
    if (status == "is-capture-possible") {
      // We handle this status in process -- don't send a message to the parent.
      gGlobalCaptureListener.requestUpdateAndNotify();
      return;
    }

    this.sendAsyncMessage("EMEVideo:ContentMediaKeysRequest", aData);
  }
}
PK