Looking at sample here
/** Your Application ID from the Google APIs Console. */
rtpg.APP_ID = YOUR_APP_ID;
I'm looking at Google API Console, I see Client ID and API key, but I can't find a field with my application id. Is it actually marked as Application ID or is it something else?
In APIs Console, go to "Overview" menu and you will find "Project Number". That is App id. I will ask for update of the documentation.