title: dragstart event gives error: Permission denied to access property "effectAllowed"
body: <p>I just started to work with meteor (1.1.0.2) and try to implement some drag and drop functionality. Basically what it should do: The user can drag video element from a sidebar to a contenteditable div.</p>
  
  <p>My problem is now that it is not working in firefox (v 37, OSX) but it is working in Chrome. </p>
  
  <p>Here is some Code:</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>Template.single_video.events(
  {
    'dragstart video': function(event)
    {
   var dt =  event.originalEvent.dataTransfer;
      dt.effectAllowed = "copy";
   dt.setData('text/html', event.currentTarget.outerHTML);
  
   return false;
    }
  })</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;template name="single_video"&gt;
   &lt;div class="col-xs-12"&gt;
    {{title}} 
    &lt;video controls="" class="video-drag" draggable="true"&gt;
     {{#each sources}}
      &lt;source src="{{src}}" type="{{type}}"&gt;
     {{/each}}
    &lt;/video&gt;
   &lt;/div&gt;
  &lt;/template&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>I always get the error: <strong>Error: Permission denied to access property "effectAllowed"</strong></p>
  
  <p>So my question is: Is it a bug in FF or did I miss something?
  Thanks in advance for any help.</p>