title: AdMob video-ad in GADBannerView is keep using CPU after a tab-change in UITabBarController
body: <p><strong>My setup:</strong> </p>
  
  <p>There's a <code>UITabBarController</code>. In the first tab - there's a <code>UINavigationController</code> with a <code>UITableViewController</code> as a root viewcontroller.</p>
  
  <p>In the table of <code>UITableViewController</code>, one of the cells contains a <code>GADBannerView</code></p>
  
  <p>In the cell with the bannerView, I'm loading the ad like this:</p>
  
  <pre><code>    var bannerView: GADBannerView = GADBannerView()
      ......
      bannerView?.adUnitID = "&lt;my adUnitId&gt;"
      bannerView?.adSize = kGADAdSizeMediumRectangle
  
      let request = GADRequest()
      request.contentURL = "&lt;my site&gt;"
      bannerView?.load(request)
  </code></pre>
  
  <p><strong>Problem:</strong></p>
  
  <p>I've noticed, that if the ad contains the video/animation - after switching between tabs - the <strong>CPU usage is still high and remains on 15-20%</strong> load forever (until you kill the app).</p>
  
  <p>Actual ad looks like this:</p>
  
  <p><a href="https://i.stack.imgur.com/HYql1.gif" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/HYql1.gif" alt="enter image description here"></a></p>
  
  <p>A couple observations:</p>
  
  <ul>
  <li>if instead of the video-ad - there's a static-image-ad - there's no issue. To me this issue looks like there's some "pause animation" which is not being called for the video-ads.</li>
  <li>happens on both iOS11 and iOS12</li>
  <li><code>func adViewDidReceiveAd(_ bannerView: GADBannerView)</code> is <strong>not</strong> being called, i.e. the framework knows that the ad is no longer on the screen</li>
  </ul>
  
  <p>This is how processes look like (after switching to another, ad-free tab):
  <a href="https://i.stack.imgur.com/OtmH3.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/OtmH3.png" alt="enter image description here"></a></p>
  
  <p><strong>Version of the AdMob:</strong></p>
  
  <p>'Firebase/AdMob', '~><strong>5.15.0</strong>' (from cocoapods)</p>
  
  <p>Any suggestions are very welcomed.</p>