Google share button callback?

Question

Google

<a target="_blank" id="mybutton" data-callback="myCallback" href="https://plus.google.com/share?url=http%3A%2F%2Fgoogle.com" data-onendinteraction="myCallback">Share on G+</a>

function start() {
// 2. Initialize the JavaScript client library.
  gapi.client.init({
  'apiKey': 'AIzaSyDDKX8UqKihNrjKYTt7DyiGNDSt-hC9src',
  // Your API key will be automatically added to the Discovery Document URLs.
  'discoveryDocs': ['https://people.googleapis.com/$discovery/rest'],
  // clientId and scope are optional if auth is not required.
  'clientId': '827352255313-h87u38in8jk064eduj5dhuk8h7qvcmng.apps.googleusercontent.com',
  'scope': 'profile',
  }).then(function() {
  // 3. Initialize and make the API request.
  return gapi.client.people.people.get({
  'resourceName': 'people/me',
  'requestMask.includeField': 'person.names'
  });
  }).then(function(response) {
  console.log(response.result);
  }, function(reason) {
  console.log('Error: ' + reason.result.error.message);
  });
};
// 1. Load the JavaScript client library.
function loadBTN(){
  gapi.load('client', start);	
  gapi.plusone.render("mybutton",{
    callback:function(jsonParam) {alert("URL: ");}
  });
}
function myCallback(jsonParam) {
  alert("URL: ");
}

You can say I'm pointing my finger at the sky. None of the alerts fire.