title: Phonegap navigator.app.backHistory / window.history.back not working on Blackberry Playbook
body: <p>On the Blackberry playbook, the normal 
  window.history.back does not work. Tested on the simulator....</p>
  
  <p>So, I attempted this in the index.html </p>
  
  <pre><code>window.history.back = navigator.app.backHistory;
  </code></pre>
  
  <p>This gives control to the Phonegap function, but at run time it throws an error: </p>
  
  <pre><code>"Error: Status=2 Message=Class App cannot be found"
  </code></pre>
  
  <p>Here is the Phonegap (1.4.1) function:</p>
  
  <pre><code>/**
   * Navigate back in the browser history.
  */
  App.prototype.backHistory = function() {
      // window.history.back() behaves oddly on BlackBerry, so use
      // native implementation.
      console.log("in backHistory");
      PhoneGap.exec(null, null, "App", "backHistory", []);
  };
  </code></pre>
  
  <p>Any clues?</p>