title: Google SignIn2 won't call the onsuccess callback
body: <p>I put a google signin button on my page using the "gapi.signin2.render" function. To this function I pass an object with the onsuccess handler.</p>
  
  <p>When the user initially clicks on the button everything works as expected. The google signin popup appears. But after finishing the signin process nothing happens on my page.</p>
  
  <p>After refreshing the page, the button triggers the auth process again. And as soon as the "Signed In" appears, the onsuccess handler gets called.</p>
  
  <p>I looked at the network traffic and saw a response containing all the information. That means that everything should be configured correctly in the google console. Otherwise I wouldn't get the response, right?</p>
  
  <p>This is my vue component:</p>
  
  <pre><code>&lt;template&gt;
    ...
    &lt;div id="google-signin-button" class="g-signin2"&gt;&lt;/div&gt;
    ...
  &lt;/template&gt;
  
  &lt;script&gt;
    ...
    window.gapi.signin2.render('google-signin-button', {
       onsuccess: this.onSignIn,
    })
    ...
    onSignIn: function(googleUser) { }
  &lt;script&gt;
  </code></pre>
  
  <p>This is the index.html:</p>
  
  <pre><code>&lt;meta name="google-signin-client_id" content="xxx.apps.googleusercontent.com"&gt;
  &lt;script src="https://apis.google.com/js/platform.js" async defer&gt;&lt;/script&gt;    
  </code></pre>
  
  <p>What can I do to get the onsuccess handler called on the initial signin?</p>