title: Blank screen after Google+ login in Android and iOS captive portal
body: <p>I've this simply google-plus login page.
  When I login from the android chrome browser all works correctly but when I try to login from the Android Captive Portal after the login I see only a blank page on the captive portal and the function onSignIn isn't executed.</p>
  
  <pre><code>&lt;html&gt;
  &lt;head&gt;
      &lt;script src="https://apis.google.com/js/platform.js" async defer&gt;&lt;/script&gt;
      &lt;meta name="google-signin-client_id" content="xxx.apps.googleusercontent.com"&gt;
      &lt;script&gt;
          function onSignIn(googleUser) {
            var profile = googleUser.getBasicProfile();
            alert('Name: ' + profile.getName());
            alert('Email: ' + profile.getEmail());
            document.getElementById("login").click();
          }
      &lt;/script&gt;
  &lt;/head&gt;
  &lt;body&gt;
      &lt;div class="g-signin2" data-onsuccess="onSignIn"&gt;&lt;/div&gt;
  
      &lt;form name="loginform" action="http://10.10.10.1/login" method="post"&gt;
        &lt;input type="hidden" name="username" value="testwifi"&gt;
        &lt;input type="hidden" name="password" value="teswifi"&gt;
        &lt;input type="submit" name="login" value="log in" id="login" style="visibility:hidden;"&gt;
      &lt;/form&gt;
  &lt;/body&gt;
  </code></pre>
  
  <p></p>