title: Saving file locally from JavaScript in WebView
body: <p>OK, here's the big picture:</p>
  
  <ul>
  <li>We have a native Cocoa/OSX app</li>
  <li>Inside this app there is a WebView</li>
  <li>Inside this WebView, there is a local web app, with its code residing in the app's bundle resources</li>
  </ul>
  
  <p>Now, the thing is:</p>
  
  <ul>
  <li>Let's say I want to save a file FROM the web app (using JS), is that possible? And how?</li>
  <li>Do I sort of have to "forward" the contents back to Objective-C/Cocoa and have the "real" app do the saving?</li>
  <li>If the first point is possible (saving from JS), what about Sandboxing? How is that to be handled?</li>
  </ul>