make it so that mathplayer message only appears when mathjax is on the page

lms/static/coffee/src/mathjax_accessible.coffee

@@ -12,5 +12,9 @@ $ ->
 	# if not, set 'aria-hidden' to 'true'
 	if MathJax? and not isMPInstalled()
 		$("#mathjax-accessibility-message").attr("aria-hidden", "false")
+
+	if MathJax? and $("#mathplayer-browser-message").length > 0
+		$("#mathplayer-browser-message").attr("aria-hidden", "false")
+		
 	else
 		$("#mathjax-accessibility-message").attr("aria-hidden", "true")

lms/templates/mathjax_accessible.html

 <%! from django.utils.translation import ugettext as _ %>
 
-<div class="sr message-accessibility message" id="mathjax-accessibility-message" aria-hidden="false">
+<div class="sr message-accessibility message" id="mathjax-accessibility-message" aria-hidden="true">
 	<p class="copy">${
 		_("This page features MathJax technology to render mathematical "
 		  "formulae. To make math accessibile, we suggest using the MathPlayer "
@@ -12,11 +12,11 @@
 	}</p>
 </div>
 
-<!--[if (lt IE6)|(gt IE 9)|!(IE)]><!-->
-<div class="sr message-accessibility message" id="mathplayer-browser-message" aria-hidden="false">
+<!--[if (lt IE 6)|(gt IE 9)|(!IE)]><!-->
+<div class="sr message-accessibility message" id="mathplayer-browser-message" aria-hidden="true">
 	<p class="copy">
 	 ${_("Your browser does not support the MathPlayer plugin. To use "
 	 	 "MathPlayer, please use Internet Explorer 6 through 9.")}
 	 </p>
 </div>
-<!--[endif]-->
+<!--<![endif]-->