Keyboard events and ARIA markup added to speed control. Replaced anonymous event…

Keyboard events and ARIA markup added to speed control. Replaced anonymous event handlers by named functions. Menu stays open on mouseleave when a speed entry has focus. In that case, the menu can be closed by clicking anywhere outside of it. [BLD-402, BLD-363]

lms/templates/video.html

@@ -71,7 +71,7 @@
                               <h3>${_('Speed')}</h3>
                               <p class="active"></p>
                           </a>
-                          <ol class="video_speeds"></ol>
+                          <ol class="video_speeds" role="menu"></ol>
                       </div>
                       <div class="volume">
                           <a href="#" title="${_('Volume')}" role="button" aria-disabled="false"></a>