title: Can't make an element scroll while scrolling to this element overlay
body: <p>I'm using <a href="http://manos.malihu.gr/jquery-custom-content-scroller/" rel="nofollow noreferrer">mcustomscrollbar</a> plugin on a specific area, and I'm having an issue when I add an overlay to this element, I can't scroll the under element. I only can scroll on a blue area, I want to scroll another area as well. I tried to trigger <code>mousewheel event</code>, but no luck.</p>
  
  <p>Any help very appreciated! <br>
  Here is the snippet with my issue:</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>(function($){
          jQuery(window).load(function(){
              jQuery(".list").mCustomScrollbar();
          });
      })(jQuery);
      
      jQuery('.list').mCustomScrollbar({ 
              theme:"dark-3"
       });
       
       $(".overlay").on("mousewheel", function(){
          jQuery(".list").trigger("mousewheel");
       })
       </code></pre>
  <pre class="snippet-code-css lang-css prettyprint-override"><code>.list{
      height: 100px;
      overflow-y: auto;
      overflow-x:  auto;
     
  }
  .overlay {
      position: fixed;
      opacity: 1;
      visibility: visible;
      top: 0;
      left: 0;
      width: 100%;
      height: 100%;
      z-index: 999;
      background-color: rgba(255, 255, 255, .5);
      -webkit-transition: opacity .15s ease-out;
      -moz-transition: opacity .15s ease-out;
      transition: opacity .15s ease-out;
  }
  
  .inner-list {
      width: 30%;
      float:left;
      background: lightblue;
      position: relative;
      z-index: 9999;
      overflow: hidden;
  }
  
  .question {
        position: absolute;
      right: 120px;
      top: 40px;
  }
  
  .row{
      list-style-type: none;
      overflow: hidden;
      width: 200px;
      height: 20px;
  }
  .row:hover{
      background-color: #E0EBEE;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.0/jquery.min.js"&gt;&lt;/script&gt;
  &lt;script src="http://malihu.github.io/custom-scrollbar/3.0.0/jquery.mCustomScrollbar.concat.min.js"&gt;&lt;/script&gt;
  &lt;link href="http://malihu.github.io/custom-scrollbar/3.0.0/jquery.mCustomScrollbar.min.css" rel="stylesheet"/&gt;
  
  
  &lt;div class="container"&gt;
  &lt;ul class="list"&gt;
      &lt;div class="inner-list"&gt;
         &lt;li class="row" id="1"&gt;1&lt;/li&gt;
        &lt;li class="row" id="2"&gt;2&lt;/li&gt;
        &lt;li class="row" id="3"&gt;3&lt;/li&gt;
        &lt;li class="row" id="4"&gt;4&lt;/li&gt;
        &lt;li class="row" id="5"&gt;5&lt;/li&gt;
        &lt;li class="row" id="6"&gt;6&lt;/li&gt;
        &lt;li class="row" id="7"&gt;7&lt;/li&gt;
        &lt;li class="row" id="8"&gt;8&lt;/li&gt;
        &lt;li class="row" id="9"&gt;9&lt;/li&gt;
        &lt;li class="row" id="10"&gt;10&lt;/li&gt;
        &lt;li class="row" id="11"&gt;11&lt;/li&gt;
        &lt;li class="row" id="12"&gt;12&lt;/li&gt;
        &lt;li class="row" id="13"&gt;13&lt;/li&gt;
        &lt;li class="row" id="14"&gt;14&lt;/li&gt;
        &lt;li class="row" id="15"&gt;15&lt;/li&gt;
        &lt;li class="row" id="16"&gt;16&lt;/li&gt;
        &lt;li class="row" id="17"&gt;17&lt;/li&gt;
        &lt;li class="row" id="18"&gt;18&lt;/li&gt;
        &lt;li class="row" id="19"&gt;19&lt;/li&gt;
        &lt;li class="row" id="20"&gt;20&lt;/li&gt;
      &lt;/div&gt;
    &lt;/ul&gt;
        &lt;p class="question"&gt;Why can't scroll here?&lt;/p&gt;
        &lt;div class="overlay"&gt;&lt;/div&gt;
  &lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>