title: Debug crashes in Handlers
body: <p>Recently my error reporting tool started to show this crash (varies slightly depending on the manufacturer of the device due to the webviews implementation)</p>
  
  <pre><code>android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
         at android.view.ViewRootImpl.checkThread(ViewRootImpl.java:4317)
         at android.view.ViewRootImpl.invalidateChild(ViewRootImpl.java:892)
         at android.view.ViewRootImpl.invalidateChildInParent(ViewRootImpl.java:941)
         at android.view.ViewGroup.invalidateChild(ViewGroup.java:4019)
         at android.view.View.invalidate(View.java:8621)
         at android.webkit.WebView.invalidate(WebView.java:1743)
         at android.webkit.WebView.viewInvalidate(WebView.java:4065)
         at android.webkit.WebView.invalidateContentRect(WebView.java:4084)
         at android.webkit.WebView.setNewPicture(WebView.java:14353)
         at android.webkit.WebView$PrivateHandler.handleMessage(WebView.java:13747)
         at android.os.Handler.dispatchMessage(Handler.java:99)
         at android.os.Looper.loop(Looper.java:137)
         at android.os.HandlerThread.run(HandlerThread.java:60)
  </code></pre>
  
  <p>I think this error comes from the Mopub's implementation (or from other ads sdk mediated with mopub) since I have no webviews in my app.</p>
  
  <p>How can I isolate and determinate if is an error I introduced or a bug in the SDK?</p>