title: Issue with Google Maps JavaScript API and ionic 2
body: <p>I'm having some troubles with the Google Maps JavaScript API used in my ionic 2 application. The first time I show the map on a page it will be rendered fine - <a href="https://i.stack.imgur.com/MXdL4.png" rel="nofollow noreferrer">see first screenshot</a>. After navigating back and opening the page with the Google Map again the map won't be rendered correctly any more. I just get a grey area instead - <a href="https://i.stack.imgur.com/2Ghrd.png" rel="nofollow noreferrer">see second screenshot</a>.</p>
  
  <p>I already searched for this issue, but nobody had a solution yet as far as I know (<a href="https://forum.ionicframework.com/t/blank-google-maps-after-navigation/51104/10" rel="nofollow noreferrer">thread with same topic here</a>)</p>
  
  <p>Maybe anyone else can help me out here?</p>
  
  <p>I also created a <a href="https://github.com/baumgarb/ionic-2-google-maps-issue" rel="nofollow noreferrer">github repository</a> which can be cloned and fired up easily so that you can reproduce the issue. Pls note that ionic 2 should be up and running if you want to try this out.</p>
  
  <p>Thanks in advance!</p>
  
  <p><a href="https://i.stack.imgur.com/MXdL4.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/MXdL4.png" alt="works fine"></a>
  <a href="https://i.stack.imgur.com/2Ghrd.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/2Ghrd.png" alt="doesnt work, just a grey area"></a></p>