Issue 2950 - Don`t rely on Services.mm, it isn`t available before Gecko 39

chrome/content/composer.js

 /*
  * This Source Code is subject to the terms of the Mozilla Public License
  * version 2.0 (the "License"). You can obtain a copy of the License at
  * http://mozilla.org/MPL/2.0/.
  */
 
 let {Prefs} = require("prefs");
 
 let domainData;
 let nodeData;
@@ skipping 475 matching lines @@
   if (advancedMode)
   {
     // Add custom CSS entry
     node = createAttribute("advanced", nodeData.customCSS, list.getAttribute("_labelcustom"), nodeData.customCSS.selected);
     list.appendChild(node);
   }
 }
 
 function togglePreview(preview, forgetNode)
 {
-  Services.mm.broadcastAsyncMessage("ElemHideHelper:Preview", {
+  let messageManager = Cc["@mozilla.org/globalmessagemanager;1"]
+    .getService(Ci.nsIMessageBroadcaster);
+  messageManager.broadcastAsyncMessage("ElemHideHelper:Preview", {
     nodeID: nodeID,
     stylesheetData: preview ? stylesheetData : null,
     forgetNode: !!forgetNode
   });
 }
 
 function changeDomain(node) {
   domainData.selected = node.getAttribute("value");
   updateExpression();
 }
@@ skipping 58 matching lines @@
 
   fillAttributes(item.nodeData);
 }
 
 function addExpression()
 {
   AdblockPlus.addPatterns([document.getElementById("expression").value]);
 
   togglePreview(false);
 }