title: Handle popups/tabs in SFSafariViewController
body: <p>I'm implementing a SoundCloud login flow in my app. The app opens <code>https://soundcloud.com/connect</code> in an <code>SFSafariViewController</code> with a <code>redirect_uri</code> that uses my app's custom URL scheme to receive the response. It works fine for direct SoundCloud logins, but fails when trying to use their "Sign in with Google" button.</p>
  
  <p>In Safari, that button opens a new tab (popup on desktop) with a Google sign-in page, which then communicates back to the SoundCloud tab via <code>postMessage</code>. This login flow works fine if you use the iOS Safari app, but fails in an <code>SFSafariViewController</code> (clicking the button goes to a white page  with a Google url: <code>https://accounts.google.com/o/oauth2/auth?...</code>).</p>
  
  <p>Right now my workaround is to advise users using Google to tap the Safari icon on the <code>SFSafariViewController</code> to complete the login flow in the Safari app, but I'm wondering if there's a way to handle this without leaving my app.</p>